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This genus, by far the largest in our flora as in most temperate regions, is composed of somewhat grass-like plants, but with clearly 3-ranked leaves. As in other Cyperaceae, the flowers are each in the axil of a single scale; however, they are unisexual. The staminate flowers consist solely of 3 stamens, and may be in separate spikes or in the same spikes as the pistillate flowers. The pistillate flowers consist solely of a pistil, with the style forked into 2 or 3 stigmas. Except for the stigmas, which protrude at flowering time, the pistil is enclosed in a sac-like or flask-shaped (but often flattened) structure called the perigynium. This is the source of many of the characters used in identification, and specimens without mature perigynia may be impossible to determine. Accurate identification also often requires the basal parts of the plant, especially rhizomes and basal sheaths.

In species with elongate spikes, perigynia from the apex or base of a spike are often less characteristic than those from the middle. In species with very short spikes, the lower perigynia are often the largest and best developed, and should be used in comparisons. Except when expressly stated to the contrary, the term “body” refers to all of the perigynium except the beak (i.e., including any narrowed base which may be present); in some groups, however, determination of where the body ends and the beak begins is somewhat difficult without a definition that is too circular—the beak beginning at the point at which the perigynium is definitely narrowed and prolonged beyond what might be expected if the body of the perigynium were beakless. This key is based on dry, pressed material and in fresh material perigynium morphology may differ considerably in some species. Members of sections Acrocystis and Laxiflorae in particular have swollen, whitish bases when fresh, which shrink dramatically when dried. As well, nerves are accentuated upon drying because of the collapse of softer tissues between the nerves.

Ligules of Carex are mostly or totally fused to the leaf blade. When ligule measurements or proportions are given, the “width” is really the same as the width of the free leaf blade at the summit of the sheath. The “length” is the total length, so that if the ligule (often in the shape of an inverted V) has a short free band at the apex but is fused to the leaf blade for most of its length, the length is the total length not just that of the free band.

Occasional exceptions to diagnostic inflorescence features occur, such as species with normally bisexual terminal spikes having them only staminate and vice-versa, species with normally single spikes bearing additional smaller spikes at the base, or depauperate, single-spiked plants of normally multiple-spiked species. Observing variation in the entire population may help in spotting such abnormalities but, in the end, no key can accommodate all such possible variations. Some common problems of interpretation are accounted for by multiple positions in the key, such as the difficult-to-interpret inflorescences of those species of section Acrocystis with basal spikes.

Many of the sections into which the genus is divided are rather uniform, mostly natural groups comprising species looking quite similar to each other; this close resemblance aids in becoming familiar with the species.

Key to Sections of Carex

1. Spike solitary, terminal (entirely staminate, entirely pistillate, or mixed).

2. Styles 2-cleft; achenes 2-sided (lenticular); basal sheaths brown.

3. Perigynia very obscurely or not at all serrulate, plump (usually at least as convex on upper face as on the lower), the lowermost tending to be remote (often as much as 0.5–1 mm distant at points of attachment); plants producing slender rhizomes; spikes without empty basal scales; anthers ca. 1.5–2.5 (–3) mm long.

Carex sect. Physoglochin

3. Perigynia minutely but strongly and regularly serrulate on apical portion and beak, ± flattened (less convex ventrally, or even plane), crowded; plants densely cespitose, not rhizomatous; spikes usually with 1–2 empty basal scales; anthers 2–3.5 mm long.

Carex sect. Stellulatae (C. exilis)

2. Styles 3-cleft; achenes 3-sided (or nearly terete); basal sheaths brown or purple-red.

4. Spikes unisexual (either staminate or pistillate); perigynia pubescent.

5. Spikes mostly (1.2–) 1.5–3.5 cm long; culms mostly exceeding leaves of current year; scales ciliate; perigynia very hairy.

Carex sect. Scirpinae

5. Spikes less than 1.5 cm long, often on short culms; scales not ciliate; perigynia minutely (and sometimes sparsely) pubescent.

Carex sect. Acrocystis (in part)

4. Spikes containing both staminate and pistillate flowers; perigynia usually glabrous.

6. Perigynia minutely pubescent.

Carex sect. Acrocystis (in part)

6. Perigynia glabrous.

7. Spikes staminate at base, pistillate toward apex, densely flowered, mostly 1 cm or more thick; perigynia inflated (i.e., much larger than the included achene), abruptly contracted to a long, very slender beak.

Carex sect. Squarrosae (in part)

7. Spikes pistillate at base, staminate above, more slender and sparsely flowered (fewer than 10 perigynia); perigynia various (but not inflated and with a long slender beak).

8. Lower pistillate scale leaf-like, at least on most spikes, much exceeding the perigynium; perigynia distinctly beaked, the body plump and filled by the mature achene.

Carex sect. Phyllostachyae (in part)

8. Lower pistillate scale not leaf-like, scarcely if at all exceeding perigynium; perigynia essentially beakless or linear-lanceolate (tapering into an indistinct beak).

9. Perigynia slender, linear-lanceolate (more than 5 times as long as thick), strongly reflexed at maturity.

Carex sect. Leucoglochin

9. Perigynia broad, less than 5 times as long as thick, appressed-ascending.

Carex sect. Leptocephalae

1. Spikes 2 or more (except rarely in depauperate individuals), sometimes crowded but distinguishable by the lobate appearance of inflorescence or protruding bracts or visible short segments of rachis between spikes. [Rarely, pistillate plants of C. scirpoidea, which normally has solitary unisexual spikes, will have small secondary spikes. Dioecious plants with strongly ciliate scales and pubescent ventral surface of the leaf sheaths should be sought at couplet 5].

10. All spikes staminate.

11. Plants with long-creeping rhizomes.

Carex sect. Divisae (C. praegracilis)

11. Plants densely cespitose.

12. Leaves flat, lax and spreading; usually swamps.

Carex sect. Deweyanae (C. bromoides)

12. Leaves channeled, stiff and erect; fens and other calcareous open habitats.

Carex sect. Stellulatae (in part)

10. At least some spikes bisexual or pistillate.

13. Styles 2-cleft; achenes 2-sided.

14. Lateral spikes peduncled, or if sessile, then elongate; terminal spike often entirely staminate.

15. Plants slender, the culms up to 2.8 (or rarely 3.7) dm tall and less than 1 mm thick (excluding leaf bases) even toward the base; terminal (staminate or sometimes mixed) spike solitary, (0.3–) 0.6–1.1 (–1.8) cm long; lowermost bract usually with a short sheath ca. 1.5–7 (rarely 10–30) mm long; perigynia white-pulverulent or golden-yellow at maturity (except in the small specimens of C. lenticularis that will run here).

16. Lowermost pistillate spike (except rarely one arising from near base of plant) sessile or nearly so; terminal spike staminate; perigynia green or slightly glaucous, crowded.

Carex sect. Phacocystis (in part)

16. Lowermost pistillate spike nearly always peduncled; terminal spike often pistillate near apex, or the pistillate spikes ± loosely flowered; fresh perigynia white-pulverulent or golden-yellow.

Carex sect. Bicolores

15. Plants coarse, the culms over (3–) 5 dm tall and usually over 1 mm thick, at least toward base; staminate spikes often 2 or more, (2–) 2.5–7 (–8) cm long; lowermost bract essentially sheathless (rarely with very short sheath); perigynia neither white-pulverulent nor golden-yellow.

Carex sect. Phacocystis (in part)

14. Lateral spikes sessile, short, often crowded; terminal spike at least partly pistillate (rarely staminate in an occasional individual).

17. Culms arising mostly singly from prominent rhizome or decumbent stolon; anthers 2–3.5 (–4) mm long (except in certain species of sect. Glareosae keyed here for added convenience).

18. Perigynia plumply plano-convex to subterete in cross-section, not winged or sharply margined; plants of sphagnum bogs, cedar swamps, etc.

19. Scales pale-hyaline with green midrib; perigynia apiculate or with very small beak; at least the lower few-flowered spikes ± separated; plants clumped from short, slender rhizomes.

Carex sect. Glareosae (in part)

19. Scales rich brown; perigynia with distinct beak ca. 0.5 mm long; spikes crowded as if in a single head; culms arising from axils of old decumbent culms (stolons).

Carex sect. Chordorrhizae

18. Perigynia strongly flattened, with distinctly winged or sharply edged margins; plants mostly of wet or dry open habitats.

20. Perigynia mostly over 2 mm wide; staminate flowers only at the base of some or all spikes.

Carex sect. Cyperoideae (including Ovales), in part

20. Perigynia mostly not over 2 mm wide; staminate flowers not restricted to base of spikes.

21. Mature perigynia with the body ± narrowly wing-margined above and the beak bidentate (firm teeth 0.5 mm long); rhizome slender (ca. 1–1.5 mm in diameter), with brownish fibrous sheaths; spikes often dissimilar, some largely or entirely staminate or pistillate, others mixed.

Carex sect. Ammoglochin

21. Mature perigynia distinctly 2-edged but not winged, the beak with short weak teeth; rhizome stout (ca. 2–3 mm in diameter), with black fibrous sheaths; spikes mostly similar (each one staminate apically and pistillate basally; in sect. Holarrhenae the upper sometimes largely staminate).

22. Sheaths of upper leaves green-nerved ventrally, usually not covering the inconspicuous nodes.

Carex sect. Holarrhenae

22. Sheaths of upper leaves with broad white-hyaline stripe on ventral side covering the included nodes.

Carex sect. Divisae (in part)

17. Culms cespitose, the tufts with or without connecting rhizomes; anthers various.

23. Staminate flowers at the base of some or all spikes, not at the apex (note especially the terminal spike).

24. Perigynia with thin-winged margins, at least narrowly so along apical part of body and basal part of beak, strongly flattened and scale-like (in some species elongate), ± appressed and overlapping (or in some species spreading at the tips).

Carex sect. Cyperoideae (including Ovales), in part

24. Perigynia at most with a ridge along the margin, not winged, the achene plumply filling at least the apical part of the body all the way to the margins.

25. Body of perigynium elliptic or nearly so (except in C. arcta) with at most a very short beak, and with rounded or slightly margined edges, nearly or entirely filled by the achene, often papillose [30–40×]; anthers 0.8–1.5 (very rarely 1.7) mm long.

Carex sect. Glareosae (in part)

25. Body of perigynium ± ovate or lanceolate or prominently beaked, sharp-edged or margined, only half to two-thirds filled by achene (very spongy around and below base of achene), not papillose; anthers 0.8–2.6 mm long.

26. Mature perigynia loosely to strongly appressed-ascending, 4–5.7 mm long; anthers (1.1–) 1.3–2.6 mm long.

Carex sect. Deweyanae (in part)

26. Mature perigynia strongly spreading to reflexed, 2–3.6 mm long; anthers 0.8–2 mm long.

27. Spikes 7–15, usually crowded, except sometimes the lowest, the inflorescence axis mostly concealed; beaks not or very obscurely bidentate.

Carex sect. Glareosae (C. arcta)

27. Spikes 3–8, not usually crowded, inflorescence axis clearly visible; beaks clearly bidentate with teeth 0.1–0.4 mm long (except for C. seorsa with smooth beaks).

Carex sect. Stellulatae (in part)

23. Staminate flowers at the apex of some or all spikes (even when anthers have fallen, protruding filaments are usually visible).

28. Culms stout (often 1.5 mm thick at ca. 3 cm below inflorescence) and very sharply angled (or even narrowly winged), ± soft and easily compressed (flattened in pressing); wider leaves 5–10 mm broad, with rather loose sheaths; perigynia spongy-thickened basally, on short slender stalks; anthers 1.3–2.6 mm long.

Carex sect. Vulpinae

28. Culms slender (not over 1.5 mm thick at ca. 3 cm below inflorescence, or rarely so in some species), firm, not wing-angled nor easily compressed (hence, not flattened in pressing); leaves, perigynia, and anthers various.

29. Spikes 10 or fewer, usually greenish at maturity, crowded or remote in a simple inflorescence (one spike, no branches, at each node of it).

30. Perigynia elliptic, essentially beakless, very plump (nearly terete) and filled by the achene; at least the lower spikes well separated, containing 1–5 perigynia.

Carex sect. Dispermae

30. Perigynia ± ovate, beaked, plano-convex or lenticular; spikes various.

31. Mature perigynia brownish; some spikes (especially terminal) entirely or mostly staminate or staminate at their bases only.

Carex sect. Stellulatae (in part)

31. Mature (not over-ripe) perigynia generally greenish; no spikes entirely or mostly staminate (a few may have stamens at their base in addition to their apex).

Carex sect. Phaestoglochin

29. Spikes numerous (10–many), yellowish or brownish at maturity; inflorescence tending to be compound, at least its lower nodes with 2 or more spikes crowded on a lateral branch.

32. Pistillate scales terminating in a distinct rough awn; bracts, at least lower ones, very slender and exceeding spikes or branches; ventral surface of leaf sheaths usually transversely wrinkled or puckered (very rarely smooth).

Carex sect. Multiflorae

32. Pistillate scales acute or minutely cuspidate; bracts mostly short, inconspicuous, or absent; leaf sheaths smooth ventrally (or sometimes wrinkled in C. decomposita).

Carex sect. Heleoglochin

13. Styles 3-cleft; achenes 3-sided (or nearly terete).

33. Perigynia at least sparsely puberulent, pubescent, hispidulous, or scabrous.

34. Perigynia ca. 12–18 mm long, in 1–2 short-oblong to spherical spikes ca. 2–3.5 cm in diameter.

Carex sect. Lupulinae (in part)

34. Perigynia ca. 2–11 mm long, in 2–5 ± elongate, cylindrical spikes less than 2 cm in diameter.

35. Perigynia with distinct and definite slender beak and/or the apex with 2 firm teeth.

36. Leaves hairy.

37. Beak of perigynium with minute, scarcely visible teeth; body of perigynium strongly 3-angled, closely enveloping the achene, essentially nerveless, tapered to a stalk-like base; culms pubescent.

Carex sect. Hirtifoliae

37. Beak of perigynium with strong spreading teeth ca. 0.8 mm or more long; body of perigynium ± rounded, loosely enveloping achene (especially at summit), strongly ribbed, ± rounded (not cuneate-tapered) at base; culms glabrous.

Carex sect. Carex (in part)

36. Leaves glabrous (often rough or scabrous, but not hairy).

38. Pistillate spikes not over 10 mm long (occasionally 12 mm in C. communis); achenes mostly with very convex or rounded sides (the angles thus obscured), at least apically, very tightly enveloped by the perigynium, especially on the apical half; anthers ca. 1.5–3.7 mm long; plants of dryish habitats.

Carex sect. Acrocystis (in part)

38. Pistillate spikes mostly over 10 mm long; achenes with flattish to slightly concave sides (the angles thus ± evident), the summit (especially around base of style) ± loosely enveloped by the perigynium; anthers ca. 2.5–4.7 mm long; plants of dry to wet habitats.

39. Perigynium beak usually more than half as long as the body, the apex not or weakly and obscurely toothed; perigynia scabrous or with short stiff ascending hairs.

40. Perigynia conspicuously 6–8 nerved; spikes densely flowered, with ca. 20–75 perigynia; basal sheaths pale brown.

Carex sect. Anomalae

40. Perigynia 2-ribbed, otherwise nerveless; spikes very loosely flowered with only 3–6 (–8) perigynia; basal sheaths reddish purple.

Carex sect. Hymenochlaenae(C. assiniboinensis)

39. Perigynium beak less than half as long as the body, with two firm apical teeth; perigynia ± densely short-hairy.

41. Perigynia 6–11 mm long, beak teeth 1.2–2.3 mm long, inner band of upper sheaths strongly purple-red tinged and thickened at apex, the thickened reddish portion opaque, smooth.

Carex sect. Carex (in part)

41. Perigynia 2.5–6.5 mm long, beak teeth 0.2–0.8 mm long, inner band of upper sheaths whitish to brown, brown- or purple-dotted, but not uniformly colored, not strongly opaque-thickened at apex, often scabrous.

Carex sect. Paludosae (in part)

35. Perigynia beakless or merely apiculate (“beak” not over 0.4 mm long) and the apex not toothed.

42. Leaf sheaths (and usually the blades) ± pubescent, especially toward base of plant; terminal spike pistillate toward apex, staminate toward base.

Carex sect. Porocystis (in part)

42. Leaf sheaths and blades glabrous; terminal spike staminate toward apex or entirely staminate.

43. Bract at base of inflorescence sheathless or nearly so, but with well-developed blade; foliage glaucous; perigynia nearly terete, in densely flowered cylindrical spikes over 1 cm long and ca. 4 mm or more thick.

Carex sect. Thuringiaca

43. Bract at base of inflorescence (not counting occasional basal spikes) usually with sheath (2–) 4 mm or more long, with blade absent or rudimentary, not over 2 (–4) cm long; foliage not glaucous; perigynia ± 3-sided, nerved or not, in spikes less than 1 cm long and/or less than 4 mm thick.

Carex sect. Digitatae (in part)

33. Perigynia glabrous (in some species, papillose or granular, but not even sparsely puberulent or scabrous).

44. Leaf sheaths (at least at apex) finely pubescent; blades often also pubescent or at least strongly hispidulous, especially toward base of plant.

45. Beak of perigynium with firm teeth ca. 1.5–3 mm long; perigynia ca. 8–10 mm long, in spikes 4–12 cm long.

Carex sect. Carex (C. atherodes)

45. Beak of perigynium with teeth scarcely 0.5 mm long or absent; perigynia less than 6 mm long, in spikes less than 3 cm long.

46. Basal sheaths pale brown, leaf blades and culms glabrous or scabrous, perigynia with ca. 50 fine, impressed nerves.

Carex sect. Griseae (C. hitchcockiana)

46. Basal sheaths reddish purple tinged, leaf blades and culms pubescent, perigynia 5–12 nerved.

47. Pistillate spikes laxly spreading or drooping on slender peduncles, the lowest (20–) 25–60 mm long (including portion inside sheath, if any); perigynia tapering to distinct beak.

Carex sect. Hymenochlaenae(in part)

47. Pistillate spikes erect or ascending, sessile, short-peduncled or on stiff, erect peduncles less than 20 (–25) mm long; perigynia beakless.

Carex sect. Porocystis (in part)

44. Leaf sheaths and blades completely glabrous (though sometimes scabrous).

48. Perigynia ± rounded to broadly tapered at summit, beakless or essentially so (the tiny beak or apiculus less than 0.5 mm long if distinct, or up to 0.8 mm long if vaguely defined, often strongly bent or curved); beak or apiculus (if present) not toothed (or teeth scarcely 0.1 mm long).

49. Leaf blades not over 0.5 mm broad, linear-filiform; perigynia dark brown or nearly black at maturity, 2 mm or less long, in few-flowered spikes, of which at least the upper ones are on peduncles usually surpassing the sessile staminate spike.

Carex sect. Albae

49. Leaf blades 0.5 mm or more broad; perigynia and spikes various (but not as above).

50. Bract of lowest pistillate spike sheathless (at most with a thin scarious sheath 1–3 mm long).

51. Terminal spike partly pistillate; pistillate spikes (except in the very local C. atratiformis) nearly or quite sessile and erect or ascending; roots glabrous or nearly so.

Carex sect. Racemosae

51. Terminal spike normally entirely staminate; spikes and roots various.

52. Pistillate spikes mostly drooping at maturity on slender peduncles; species of wet peat lands with roots with dense felt-like pubescence (if roots lack felt-like pubescence and plants are from mineral soil, check C. flacca).

Carex sect. Limosae

52. Pistillate spikes erect or ascending, sessile or peduncled; roots glabrous.

53. Perigynia 2.5–3.4 mm wide; leaves involute, 0.5–2.5 mm wide.

Carex sect. Vesicariae (C. oligosperma)

53. Perigynia 1–2.5 mm wide; leaves flat or folded, 1–35 mm wide.

go to couplet 57

50. Bract of lowest pistillate spike with a sheath ca. 4 mm or more long.

54. Terminal spike bearing some perigynia (very rarely a few individuals with one entirely staminate); plants very strongly reddish tinged at base.

55. Staminate flowers at apex of terminal spike, pistillate flowers at base; cauline sheaths bladeless or with rudimentary blades up to 2 (rarely 4) cm long; pistillate spikes short-cylindric, bearing fewer than 10 perigynia, very long-peduncled, some elongate peduncles usually arising from base of plant.

Carex sect. Digitatae(C. pedunculata)

55. Staminate flowers at base of terminal spike, pistillate flowers at apex; cauline sheaths with well-developed blades; pistillate spikes linear-cylindric, bearing more than 10 perigynia, on peduncles about as long as the spike or shorter, all arising from the upper part of the culm.

Carex sect. Hymenochlaenae(in part)

54. Terminal spike entirely staminate; plants reddish or not at base.

56. Perigynia concave- or at least cuneate-tapering toward the base, ± 3-angled and often somewhat broadly spindle-shaped.

57. Plants with elongate deep or shallow rhizomes; leaf blades ca. 1–4 mm wide.

Carex sect. Paniceae(in part)

57. Plants cespitose, without elongate rhizomes; leaf blades usually more than 4 (and up to 35) mm wide (except in the woodland Carex digitalis).

58. Perigynia rounded-triangular in cross-section; culms sharply triangular, sometimes nearly wing-margined, rather weak and easily compressed, soon shriveling after maturity of the fruit.

Carex sect. Laxiflorae (in part)

58. Perigynia ± sharply triangular with flattish sides; culms bluntly trigonous, firm and not easily compressed.

Carex sect. Careyanae (in part)

56. Perigynia convex-rounded toward the base, nearly or quite circular in cross-section (or very obscurely triangular), ellipsoid-cylindric to nearly spherical.

59. Larger perigynia ca. 4–5 mm long, the nerves not raised above the surface at maturity.

Carex sect. Griseae (in part)

59. Larger perigynia ca. 2–3.5 mm long; nerves various.

60. Perigynia with the nerves not raised above the surface, usually ± impressed; staminate spike usually long-peduncled; plants not strongly rhizomatous nor with any pistillate spikes on basal peduncles.

Carex sect. Griseae (C. conoidea)

60. Perigynia with the nerves slightly raised above the surface; staminate spike nearly or quite sessile or, if long-peduncled, the plants strongly rhizomatous and with basal pistillate spikes.

Carex sect. Granulares

48. Perigynium abruptly contracted or more gradually tapering to a definite slender beak 0.5 mm or more long, or to an indistinct tapering beak 1 mm or more long; beak in some species with short apical teeth.

61. Body of perigynium obovoid or obconic, ± truncately contracted into a distinct long slender beak; terminal spike often mostly pistillate (staminate at base only).

Carex sect. Squarrosae (in part)

61. Body of perigynium ovoid to lanceolate or ellipsoid, tapered or contracted into the beak; terminal spike usually staminate, at least apically.

62. Lower pistillate scales leaf-like or bract-like, much exceeding the perigynia; achenes abruptly constricted to a short thick base; body of perigynium nearly terete, essentially nerveless except for 2 ribs; anthers ca. 0.5–1.6 mm long.

Carex sect. Phyllostachyae (in part)

62. Lower pistillate scales scarcely if at all exceeding the perigynia; achenes not abruptly constricted at the base; perigynia and anthers various.

63. Perigynia spreading and with the lowermost usually reflexed, in densely crowded spherical to very short-cylindric spikes, usually strongly few-ribbed; at least the uppermost pistillate spikes ± sessile and often crowded; the terminal spike (staminate or partly pistillate) often sessile or short-peduncled.

64. Perigynia 2–6.2 mm long; basal sheaths brown.

Carex sect. Ceratocystis

64. Perigynia 11–18 mm long; basal sheaths reddish purple tinged.

Carex sect. Lupulinae (in part)

63. Perigynia ascending or reflexed, but in elongate and/or long-peduncled cylindrical spikes, upper spikes crowded or not, perigynia 2-ribbed or variously many-nerved;the terminal spike often long-peduncled.

65. Bract of lowest pistillate spike sheathless (or pistillate spikes all crowded at base of plant in Carex tonsa) (check several stems; rarely, a pistillate spike will be borne abnormally low on the culm and this spike may then have a sheath, which should be disregarded in keying.

66. Pistillate scales subtending at least some of the perigynia terminated by a distinct slender scabrous awn; perigynia ca. 3–9 mm long.

67. Scales toward apex of pistillate spikes merely acuminate or with awns shorter than their bodies (the latter easily visible, about half as long as perigynia or longer); staminate spikes 2 or more; body of perigynium rather gradually tapered to a beak ca. 1.5 mm long, including the short (not over ca. 0.8 mm) teeth.

Carex sect. Paludosae (in part)

67. Scales toward apex of pistillate spikes ordinarily with awns (as on the other pistillate scales) nearly or fully as long as their bodies (the latter small and mostly hidden among the bases of the densely crowded perigynia); staminate spike solitary (or very rarely a second smaller one present); body of perigynium tapered or strongly contracted into a beak ca. 1.2–3.5 mm long, including teeth up to 2.2 mm long.

Carex sect. Vesicariae (in part)

66. Pistillate scales smooth-margined and awnless or very short-awned, or at most with a scabrous margin toward an acuminate (sometimes inrolled) apex (occasionally a long rough awn in species with perigynia more than 9 mm long); perigynia (4–) 4.5–18 mm long.

68. Basal sheaths pale brown; perigynia very narrowly lanceolate, 4–6.5 times as long as wide and not over 3 mm wide, many-nerved, tapering to apex (not strongly contracted into a beak); staminate spike solitary (pistillate spikes may be staminate at apex).

Carex sect. Rostrales

68. Basal sheaths reddish purple tinged, at least on the youngest shoots; perigynia lanceolate or broader, less than 4 times as long as wide, or more than 3 mm wide, or strongly contracted into a conspicuous beak (or all of these); staminate spikes solitary or 2 or more.

69. Perigynia ± strongly inflated, not tightly wrapped around achene, (1.7–) 2–8 mm wide.

70. Perigynia 4–12 mm long, ca. 6–12 (–15)-nerved.

Carex sect. Vesicariae (in part)

70. Perigynia (11–) 12–17 (–18) mm long, ca. 15–20-nerved.

Carex sect. Lupulinae (in part)

69. Perigynia not inflated, ± tightly enclosing achene, 1–1.6 mm wide.

71. Pistillate spikes linear-cylindric, drooping or curving on slender peduncles; perigynia (somewhat twisted) and achenes strongly angled, the latter with concave sides; tall plants (culms over 3 dm high) with scattered thin leaves.

Carex sect. Hymenochlaenae (C. prasina)

71. Pistillate spikes short, thick, and few-flowered, often crowded at base of plant; perigynia and achenes very convex-sided; low plants (culms less than 1 dm high) with crowded, very stiff leaves.

Carex sect. Acrocystis (C. tonsa var. tonsa)

65. Bract of lowest pistillate spike consistently with sheath 4 mm or more long.

72. Perigynia (6–) 9–17 (–18) mm long; beak teeth usually conspicuous and stiff.

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72. Perigynia 2–6.5 (–9) mm long; beak teeth absent or weak and inconspicuous.

73. Perigynia with several to numerous conspicuous fine nerves the full length of each side.

74. Nerves of perigynia very numerous (ca. 20–65) and impressed, giving a longitudinally corrugated appearance; awns of pistillate scales rough or even ciliate.

Carex sect. Griseae (in part)

74. Nerves of perigynia several to many (ca. 5–40) and slightly raised; awns of pistillate scales absent, smooth, or rough.

75. Awns scabrous-ciliate and/or summit of pistillate scales minutely ciliate; lower spikes drooping on long very thin peduncles; beak slightly bidentate at maturity; plants strongly reddish at base.

Carex sect. Hymenochlaenae (in part)

75. Awns of pistillate scales usually smooth or absent; lower spikes mostly not drooping; beak not bidentate; plants pale, brown, or reddish at base.

76. Perigynia ± sharply triangular with flattish sides, short-tapering at the base; culms bluntly trigonous, firm and not easily compressed; anthers mostly 3–4.5 mm long or lower pistillate spikes on elongate filiform spreading or drooping peduncles.

Carex sect. Careyanae (in part)

76. Perigynia ± rounded-triangular with swollen sides, long-tapering to a ± stalk-like base; culms sharply triangular to nearly wing-margined, easily compressed; anthers mostly 1.5–3 mm long and lower pistillate spikes usually on erect or ascending peduncles.

Carex sect. Laxiflorae (in part)

73. Perigynia with 2 (–3) main ribs, the sides otherwise nerveless or with much less prominent nerves.

77. Lowermost pistillate spikes erect or ascending at maturity.

78. Staminate spike well-peduncled; perigynia ± convex-sided toward the base; bracts with poorly developed blades; plants mat-forming from long-creeping rhizomes.

Carex sect. Paniceae (C. vaginata)

78. Staminate spike sessile or nearly so; perigynia tapered-cuneate toward the base; bracts with well-developed blades; plants cespitose.

Carex sect. Laxiflorae (C. leptonervia)

77. Lowermost pistillate spikes drooping on long very thin peduncles at maturity.

79. Pistillate spikes not over 15 mm long.

Carex sect. Chlorostachyae

79. Pistillate spikes mostly 20 mm or more long.

Carex sect. Hymenochlaenae (in part)


CAREX SECT. ACROCYSTIS (Montanae of Michigan Flora)

1. Pistillate spikes on culms of varying length, at least some of the culms short (up to ca. 5 cm long) and partly hidden among the tufted leaf bases [be sure to sample a population adequately]; anthers ca. 1.5–2 mm long.

2. Bract of the lowest non-basal pistillate spike leaf-like, equaling or exceeding the tip of the staminate spike; remnants of old leaves only slightly breaking into fibrous shreds at the base.

3. Perigynia ca. 3–3.5 mm long, including a beak ca. 1 mm or a little longer (or only 0.5 mm in some basal spikes); staminate spikes ca. 5–12 mm long; rhizomes very stout.

C. rossii

3. Perigynia ca. 2–2.7 (–3) mm long, the beak ca. 0.4–0.6 mm; staminate spikes 2–2.5 mm long, often very inconspicuous; rhizomes slender.

C. deflexa (in part)

2. Bract of the lowest non-basal pistillate spike scale-like or bristle-like, not exceeding the staminate spike (or all spikes often on short basal culms, but foliage and culms stiffer and much more scabrous than in C. rossii and C. deflexa, which nearly always have some elongate culms); remnants of old leaves breaking into copious fibrous shreds at the base.

4. Perigynia (3–) 3.2–4 mm long, the beak 1.2–1.6 (–2) mm, about half as long as the body or longer.

C. tonsa

4. Perigynia 2.5–2.9 mm long, the beak 0.4–0.9 mm, about 1/4–1/3 (rarely 1/2) as long as the body.

C. umbellata

1. Pistillate spikes all on elongate culms (none borne on short basal peduncles); anthers various.

5. Main body of perigynium, not including spongy-tapered base or beak, orbicular to short-obovoid, about the same diameter as length; anthers 2.1–3.7 mm long; plants either with the widest leaves 3–8 mm broad or with elongate shallow rhizomes.

6. Widest leaves (at least the oldest dry ones) (3–) 3.3–5 (–8) mm broad; cauline leaves above base of plant (when present on culm) usually with the ligule longer than the width of the leaf; bract subtending the middle (and sometimes the lowest) pistillate spike(s) ± scarious-lobed at base, blade awn-like to leaf-like, usually green, arising from between the lobes; staminate spike ca. 1–2 (–2.5) mm thick; plants without elongate rhizomes.

C. communis (in part)

6. Widest leaves 1.5–2.9 (very rarely 3.5) mm broad; cauline leaves with ligule no longer than the width; bracts subtending middle pistillate spikes tapered to apex, without an elongate awn-like or leaf-like blade (the lowermost bract often green but seldom lobed); staminate spike ca. 2–3.5 (–5) mm thick; plants with stout, shallow elongate rhizomes with fibrous sheaths.

7. Larger perigynia 1.7–2.2 mm wide; upper staminate scales acuminate to long-acuminate; very rare.

C. inops

7. Larger perigynia 1.2–1.7 mm wide; upper staminate scales acute to acuminate; common species.

8. Beak of perigynium 1–1.6 mm, half or more as long as the body.

C. lucorum

8. Beak of perigynium 0.2–0.8 mm, much less than half as long as the body.

C. pensylvanica

5. Main body of perigynium ± elliptic (to slightly obovoid or oblong), definitely longer than thick; anthers ca. 1.3–2.2 (–2.5) mm long; plants with mostly narrow leaves and lacking stout elongate rhizomes (and otherwise not fitting either lead of couplet 6).

9. Widest leaves (at least the oldest dry ones) (3–) 3.3–5 (–8) mm broad; bract subtending the middle (and sometimes also the lowest) pistillate spike(s) ± scarious-lobed at base, the blade awn-like to leaf-like, usually green, arising from between the lobes.

C. communis (in part)

9. Widest leaves not over 3 mm broad; bracts either scale-like or leaf-like and lacking a scarious-lobed base.

10. Lower two pistillate spikes 7.5–22 mm distant; lowest inflorescence bracts 18–35 mm long, 3/4 as long to exceeding inflorescence; loosely mat-forming from delicate, ascending rhizomes.

C. novae-angliae

10. Lower two pistillate spikes mostly close together, up to 7 mm distant; lowest inflorescence bracts rarely more than 17 mm long, often less than 3/4 as long the inflorescence; ± cespitose.

11. Bodies of mature perigynia about as long as their scales or even slightly shorter; beak of perigynium ca. 0.5–1.4 mm long.

C. albicans

11. Bodies of mature perigynia mostly distinctly exceeding their scales; beak of perigynium ca. 0.4–0.7 mm long.

12. Perigynia ca. 2–2.7 (–3) mm long, minutely puberulent to short-hairy; culms very slender (seldom over 0.4 mm thick) and mostly surpassed by the leaves.

C. deflexa (in part)

12. Perigynia ca. 3–3.8 mm long, definitely short-hairy; culms mostly 0.5–0.8 mm in thickness and surpassing the leaves.

C. peckii


C. eburnea

CAREX SECT. AMMOGLOCHIN (Arenariae of Michigan Flora)

C. siccata


C. scabrata


1. Mature perigynia golden-orange when fresh (drying dark brown or, especially if immature, ± white-pulverulent); terminal spikes mostly all staminate (occasionally with a very few perigynia); pistillate scales ± loosely spreading, distinctly shorter than the mature perigynia (usually averaging 3/4 or less as long), most of them acute to cuspidate.

C. aurea

1. Mature perigynia white-pulverulent when fresh; terminal spikes usually staminate at base only, with several to numerous perigynia apically; pistillate scales ± appressed, nearly (averaging about 3/4) to quite as long as the perigynia, most of them blunt to acute.

C. garberi


The tall vegetative shoots of this section of large wetland plants are true culms with nodes and internodes, and readily recognized once learned.

1. Inner band of sheaths glabrous, the apex strongly purple-red tinged and thickened at apex, the thickened reddish portion opaque, glossy, and nerveless; leaf blades glabrous.

C. trichocarpa

1. Inner bands of sheaths pubescent apically, the apex brownish or sometimes brown or red dotted, not thickened or shiny, with evident veins; leaf blades often with long spreading hairs, at least abaxially.

2. Perigynia glabrous or sometimes with scattered spreading hairs on the main veins of the beaks, (6.5–) 7–12 mm long; longest beak teeth (1.2–) 1.5–3 mm long.

C. atherodes

2. Perigynia pubescent, 4.4–7.8 mm long; longest beak teeth 0.6–1.7 mm long.

C. hirta

CAREX SECT. CAREYANAE (Included in Laxiflorae in Michigan Flora)

1. Larger leaf blades (especially on vegetative shoots) mostly 12–40 mm broad (or if largest blades as narrow as 8 mm, the bases of plants and the staminate scales strongly reddish).

2. Bases of plants and staminate scales pale or brownish, not reddish; perigynia 2.6–4.2 mm long.

C. platyphylla

2. Bases of plants and staminate scales strongly tinged with reddish; perigynia 4–6.5 mm long.

3. Sheaths of cauline bracts and leaves bladeless or nearly so; perigynia (3.5–) 4–5 mm long.

C. plantaginea

3. Sheaths of cauline bracts and leaves with flat green blades; perigynia (3.7–) 5–6.5 mm long.

C. careyana

1. Widest leaf blades 2.5–11.5 mm wide; plant bases brownish.

4. Pistillate spikes (except sometimes the upper ones) with 1–2 staminate flowers at the base; leaves green or glaucous, 4.5–11.5 mm broad.

C. laxiculmis

4. Pistillate spikes without staminate flowers at the base; leaf blades deep or bright green, the wider ones 2.5–4 (–5) mm broad.

C. digitalis

CAREX SECT. CERATOCYSTIS (Extensae of Michigan Flora)

Hybrids seem to be commoner in this section than in most groups of Carex. Carex flava × C. viridula (C. ×alsatica Zahn) is especially likely to occur wherever the parents grow together. It is sterile, ± intermediate morphologically, and sometimes shows hybrid vigor, forming large clumps.

1. Larger perigynia ca. 2–3 mm long, horizontally spreading, the beak about a fourth to nearly half as long as the body.

C. viridula

1. Larger perigynia ca. (3–) 3.5–6.2 mm long, at least the beaks becoming conspicuously reflexed on lower half of spike, the beak nearly or fully half as long as the body.

2. Pistillate scales at maturity strongly flushed with shiny brown or reddish color, hence conspicuous in the spike; widest leaves (2.5–) 3–5 mm wide.

C. flava

2. Pistillate scales greenish or yellowish, the same color as the perigynia and essentially invisible in the spikes; widest leaves 1.5–3.8 mm wide.

3. Larger pistillate spikes 7–9.5 (–10.5) mm wide; perigynium beaks 1.3–2.3 mm long, completely smooth.

C. cryptolepis

3. Larger pistillate spikes 10.5–14 mm wide; perigynium beaks 2.2–2.8 mm long, at least some on a plant very sparsely serrulate.

C. viridistellata


Capillares of Michigan Flora.

C. capillaris


C. chordorrhiza


This is a very complex group, and identification is especially difficult. Mature perigynia are absolutely essential. In many species with normally elongated and often nodding inflorescences, flowering shoots produced after the primary flush of growth in spring have abnormally congested inflorescences and may be very difficult to key. Papillae on leaf sheaths may require close examination, and are often seen best on dried material, as are nerves on perigynia. A number of species are abundant and commonly encountered, but many are uncommon to rare plants of highly specialized habitats. The section is characterized by vegetative shoots which are true culms, with nodes and internodes, in contrast to the vegetative shoots of most species of Carex, where the stem-like portion is formed only of overlapping leaf sheaths, and lacks nodes and internodes. This feature, combined with the cespitose habit and brownish basal sheaths, is diagnostic for the section, and allows it to be recognized even in vegetative condition. In some species, the vegetative shoots are long and leafy (though developing fully only after the fruits mature) and may function in vegetative reproduction (i.e., C. tribuloides, C. projecta, C. longii, and rarely other species).

1. Bracts leaf-like, the broadest 2–4 mm wide, many times exceeding the spikes (which are crowded in a dense head); perigynia very narrowly lanceolate, not over 1 mm wide.

C. sychnocephala

1. Bracts not resembling the leaves, narrower than 2 mm most or all their length and not over twice as long as the inflorescence; perigynia various.

2. Pistillate scales about or fully as long as the perigynia and nearly the same width as the beaked portion (not necessarily the body), so that the apical portion of each perigynium is largely concealed; anthers ca. 1.5–3 mm long.

3. Perigynia lanceolate, ca. 1.5 mm broad, the beak prominently slender and at the very tip nearly terete, hyaline, and smooth-margined; body ± membranous and nerveless ventrally.

C. praticola

3. Perigynia ± ovate, more than 1.5 mm broad, the beak flattened and serrulate to the tip; body usually firmer and often at least sparsely nerved ventrally.

4. Inflorescence stiff, the spikes close together, mostly overlapping; pistillate scales nearly as wide as the bodies of the perigynia, almost concealing them.

C. adusta

4. Inflorescence ± lax or flexuous, the lowermost spikes usually remote; pistillate scales distinctly narrower than bodies of perigynia (the wings of which clearly protrude at maturity).

5. Perigynia whitish green throughout, even in maturity, strongly and evenly nerved on ventral face, finely granular-papillose, with the wing often broadened and ± undulate or erose at the junction of beak and body; spikes mostly 7–15, the distal usually crowded.

C. argyrantha

5. Perigynia at maturity brownish, at least in basal half, often nerveless on ventral face or with few nerves of unequal strength, smooth, the wing without a broadened undulate or erose area; spikes mostly 3–7, the distal often ± separated.

C. foenea

2. Pistillate scales (or most of them) both shorter and narrower than beaks of perigynia, so the mature perigynia are largely exposed apically; anthers various.

6. Pistillate scales in the middle or lower portions of the spikes acuminate with a subulate tip or awned.

7. Perigynia 2.6–4 times as long as wide, the bodies lanceolate; 0.9–2 mm wide.

8. Perigynia 0.9–1.2 mm wide; achenes 0.6–0.8 mm wide; inflorescences dense, lowest inflorescence internodes 2–3 (–5) mm long.

C. crawfordii (in part)

8. Perigynia 1.2–2.0 mm wide; achenes 0.7–1.1 mm wide; inflorescences dense to open or flexuous, lowest internodes 2–17 mm long.

C. scoparia (in part)

7. Perigynia, less than 2.5 times as long as wide, the bodies lance-ovate, ovate, broadly elliptic, orbicular, or obovate; 1.8–3.9 mm wide.

9. Perigynium bodies strongly obovate, often with conspicuous “shoulders,” abruptly contracted into the beak; broadest leaves 2.5–6 mm wide.

C. alata

9. Perigynium bodies elliptic, suborbicular, rhombic, or weakly obovate, gradually tapered to gently contracted into the beak; broadest leaves 1.5–3 (–3.7) mm wide.

10. Perigynium bodies cuneately tapering to the base, the base therefore subacute and the body ± diamond shaped; inflorescences ± compact, stiffly erect, with 3–5 spikes.

C. suberecta (in part)

10. Perigynium bodies rounded to the base, the body therefore elliptic, orbicular or weakly obovate; inflorescences elongate and nodding, the larger with 5–7 spikes.

C. straminea


6. Pistillate scales obtuse, acute or acuminate, sometimes inconspicuous in the spikes.

11. Perigynia (6.5–) 7–9 mm long; larger spikes on each culm ca. 1.5–2.5 cm long and 1/5–1/3 as thick in the middle, tapered to both ends.

C. muskingumensis

11. Perigynia shorter; spikes usually shorter and a third or more as thick as long.

12. Mature perigynia more than 2 mm broad at widest part.

13. Perigynium bodies obovate, widest above the middle; leaf sheaths green-nerved ventrally nearly to the summit with at most a narrow V-shaped hyaline area.

14. Perigynium beaks spreading, slender and abruptly contracted from the body, the distance from beak tip to top of achene 1–2 mm; styles with strong lateral sinuosity at the base.

C. albolutescens (in part)

14. Perigynium beaks appressed-ascending, triangular and gradually tapered from the body or the distance from beak tip to top of achene 2 mm or more; styles straight or occasionally sinuous near middle.

15. Perigynia nerveless on ventral face; broadest leaves 3–6 (–8) mm wide, their sheaths truncate at summit and extending 0.3 mm above base of leaf blade.

C. cumulata

15. Perigynia nerved on ventral face; broadest leaves 2–4 mm wide, their sheaths concave at summit and not prolonged above base of leaf blade.

C. longii (in part)

13. Perigynium bodies lanceolate, ovate, elliptic, or orbicular, widest at or below the middle; leaf sheaths with prominent hyaline band near the apex ventrally (except in C. suberecta, with diamond-shaped perigynia (see couplet 16).

16. Leaf sheaths green-nerved ventrally nearly to the summit; perigynia cuneately tapering to the base, the body therefore ± diamond-shaped.

C. suberecta (in part)

16. Leaf sheaths with a white hyaline area ventrally; perigynia rounded to the base, the bodies therefore ovate, elliptic, or orbicular.

17. Perigynium bodies narrowly to broadly ovate, greenish, gradually tapered to the beak; pistillate scales with a green midstripe and hyaline or pale margins, rarely brown tinged; leaves 2.5–6.5 mm wide, the sheaths green-mottled, the mouth of sheaths truncate and prolonged up to 2 mm above the base of leaf blades.

C. normalis (in part)

17. Perigynium bodies broadly ovate, broadly elliptic, or orbicular, yellowish to tan brown, often abruptly contracted to the beak; pistillate scales greenish to dark brown; leaves 1.5–4 (–5) mm wide, the sheaths evenly colored, the mouth of sheaths concave (prolonged above base of leaf blades in C. merritt-fernaldii).

18. Leaf sheaths finely papillose at high magnification [30–40×], especially near the leaf base.

19. Perigynia strongly and evenly 4–8-nerved over the achene on the ventral face, (4.5–) 5.1–6.7 mm long, pistillate scales usually (1–) 1.4–2.3 mm shorter than the perigynia; anthers (2.4–) 2.8–4.2 mm long.

C. bicknellii

19. Perigynia nerveless or faintly and irregularly 0–5 (–6)-nerved over the achene on the ventral face, (2.3–) 2.5–5.2 (–5.5) mm long, pistillate scales 0.2–1.3 mm shorter than the perigynia; anthers (1–) 1.3–2.6 mm long.

20. Pistillate scales dark rust or brown; leaves of fertile shoots 2–4, the leaf sheaths with ventral hyaline area sometimes puckered or cross-corrugated.

C. tincta (in part)

20. Pistillate scales greenish to yellowish; leaves of fertile shoots 3–6, the leaf sheaths not puckered.

21. Perigynia 2.5–3.4 mm wide; achenes 1.3–1.5 mm wide.

C. merritt-fernaldii

21. Perigynia 2–2.4 (–2.6) mm wide; achenes (0.9–) 1–1.3 mm wide.

C. festucacea (in part)

18. Leaf sheaths smooth.

22. Spikes on larger inflorescences 2–4 (rarely more), rounded at the base, the terminal one lacking a conspicuous staminate base; inflorescences mostly 1.3–3 cm long (the lowest internodes generally 1.5–6 mm long); perigynium bodies elliptic to ovate (rarely orbicular), 1–1.6 times as long as wide.

C. molesta (in part)

22. Spikes on larger inflorescences (4–) 5–7 or more, tapered at the base, the terminal one with a conspicuous staminate base; inflorescences typically 2.5–4.5 (–6) cm long (the lowest internodes generally 5–13 mm long); perigynium bodies broadly ovate to orbicular, (0.7–) 0.9–1.2 times as long as wide.

23. Larger perigynia 2.5–3.3 (–3.5) mm wide, the ventral face usually nerveless; larger achenes 1.4–1.8 mm wide.

C. brevior

23. Larger perigynia 1.5–2.4 (–2.6) mm wide, the ventral face mostly 2–4-nerved; larger achenes 0.9–1.3 mm wide.

C. festucacea (in part)

12. Mature perigynia not over 2 mm broad.

24. Perigynia thin, ± scale-like, often not winged to the base; leaf sheaths somewhat expanded towards apex and bearing narrow wings continuous with midrib and edges of leaf blade, blades 3–7 mm wide; vegetative shoots tall, conspicuous, and with numerous leaves spaced along upper 1/2 of culm.

25. Perigynia stiffly spreading or recurved; spikes ± spherical; pistillate scales hidden, 1.6–2.4 mm long.

C. cristatella

25. Perigynia loosely spreading or appressed-ascending; spikes nearly spherical to ovate-oblong; pistillate scales evident, 2–3 mm long.

26. Inflorescences stiff, typically erect, spikes overlapping; perigynia usually more than 40 per spike, beaks appressed-ascending; leaf sheaths firm at summit.

C. tribuloides

26. Inflorescences flexuous, arching or nodding when well-developed, with the lower spikes usually separated; perigynia usually 15–40 per spike, the beaks spreading; leaf sheaths firm or friable at summit.

C. projecta

24. Perigynia thicker, plano-convex, winged to the base; leaf sheaths with ± rounded edges, not distinctly expanded towards apex, blades 1–4.5 mm (–5) wide (except in C. normalis); vegetative shoots usually inconspicuous, with leaves relatively few and clustered at apex.

27. Perigynia 2.6–4 times longer than wide, the bodies lanceolate, the distance from beak tip to top of achene 2.2–5.0 mm (as little as 1.8 mm long in C. crawfordii with perigynia less than 1.2 mm wide).

28. Perigynia 0.9–1.2 mm wide; achenes 0.6–0.8 mm wide; inflorescences dense, lowest inflorescence internodes 2–3 (–5) mm long.

C. crawfordii (in part)

28. Perigynia 1.2–2 mm wide; achenes 0.7–1.1 mm wide; inflorescences dense to open or even flexuous, lowest internodes 2–17 mm long.

29. Inflorescences dense or open, spikes usually overlapping; pistillate scales acuminate; perigynia usually ascending.

C. scoparia (in part)

29. Inflorescences nodding or flexuous, spikes well separated; pistillate scales acute; perigynia spreading.

C. echinodes (in part)

27. Perigynia less than 2.5 times longer than wide, the bodies obovate, orbicular, or ovate, the distance from beak tip to top of achene 0.8–2.2 mm.

30. Perigynium bodies obovate, widest above the middle of the body.

31. Perigynium beaks appressed-ascending, triangular and gradually tapered from the body; pistillate scales obtuse; styles straight.

C. longii (in part)

31. Perigynium beaks spreading, slender and abruptly contacted from the body; pistillate scales acute; styles with strong lateral sinuosity at the base.

C. albolutescens (in part)

30. Perigynium bodies ovate, elliptic, or orbicular, widest at or below the middle of the body.

32. Inflorescences on tallest culms compact, ca. 1.5–3 times as long as wide, erect, the spikes overlapping; lowest inflorescence internodes 1–6 (–7.5) mm long, 1/12–1/5 (–1/4) the total length of the inflorescence.

33. Achenes 0.6–0.9 mm wide; perigynia nerveless or with 1–3 faint or basal nerves on the ventral face; inflorescences less than 30 mm long.

C. bebbii

33. Achenes 0.9–1.3 mm wide; perigynia often with 3 or more well-defined ventral nerves; inflorescences 12–60 mm long.

34. Perigynium body broadly elliptic, or nearly orbicular, with wing margin 0.4–0.8 mm wide, conspicuous ventral nerves 0–6.

C. molesta (in part)

34. Perigynium body ovate to broadly ovate, their wing margins 0.2–0.4 mm wide, ventral nerves 4–7.

35. Sheaths smooth, whitish mottled, the inner band not corrugated; perigynia greenish at maturity.

C. normalis (in part)

35. Sheaths finely papillose [30–40×], (most easily seen near the leaf base) not whitish mottled, the inner band sometimes corrugated; perigynia pale brown at maturity.

C. tincta (in part)

32. Inflorescences on tallest culms elongate, ± open proximally, ca. (2.5–) 3–5.1 times as long as wide, often arching or nodding; lowest inflorescence internodes (5–) 7–19 mm long, mostly 1/5–1/3 (–1/2) the total length of the inflorescence.

36. Perigynium bodies orbicular, widest at the middle and abruptly contracted into the beak.

C. festucacea (in part)

36. Perigynium bodies narrowly to broadly ovate, widest below the middle and tapering to contracted into the beak.

37. At least some sheaths papillose near the collar [30–40×], not prominently whitish mottled; perigynium beaks appressed or ascending in the spikes, exceeding pistillate scales by 0–0.8 mm; beaks and shoulders of perigynia stramineous to reddish brown at maturity.

C. tenera

37. Sheaths totally smooth, often whitish mottled; perigynium beaks spreading, mostly exceeding pistillate scales by (0.6–) 0.7–1.6 mm; beaks and shoulders of perigynia greenish to yellowish or greenish brown at maturity.

38. Inflorescences erect to somewhat bent, the lowest internodes mostly 6–10 (–11.5) mm long, the rachis stiff; leaves 2.2–6.5 mm wide; larger perigynia mostly 3.1–3.8 (–4) mm long and 1.8–2.2 times as long as wide; plants forming small, ± erect clumps often with fewer than 20 culms.

C. normalis (in part)

38. Inflorescences arching or nodding, the lowest internodes (6–) 10–21 mm long, the rachis usually thin and wiry; leaves 1.5–3.5 (–3.7) mm wide; larger perigynia mostly (3.4–) 3.6–4.6 mm long, (1.9–) 2.1–2.8 (–3.2) times as long as wide; plants often forming large, spreading clumps of more than 30 culms.

C. echinodes (in part)


1. Perigynia ca. 0.8–1.2 mm wide and ca. 4–5 times as long as wide, conspicuously nerved on dorsal face, weakly to strongly nerved on ventral face.

C. bromoides

1. Perigynia ca. 1.3–1.6 mm wide and usually ca. 3–3.5 times as long as wide, faintly nerved or nerveless on both faces.

C. deweyana


1. Terminal spike pistillate at base; basal spikes usually present, on long very thin peduncles; pistillate scales abruptly truncate and awned; anthers (1.6–) 2–3 mm long.

C. pedunculata

1. Terminal spike usually entirely staminate; basal spikes not present; pistillate scales obtuse or acuminate, not awned; anthers various.

2. Staminate spike ca. 4–6 (–8) mm long; pistillate spikes less than 10 mm long; pistillate scales obtuse, minutely ciliate, distinctly shorter than the perigynia; anthers ca. 1–1.5 mm long.

C. concinna

2. Staminate spike ca. 10–22 mm long; pistillate spikes (often staminate at their tips) ca. (8–) 10 mm long; pistillate scales mostly acute to acuminate, glabrous, and equaling or exceeding the perigynia; anthers ca. (1.7–) 2–3.5 mm long.

C. richardsonii

CAREX SECT. DISPERMAE (Included in Heleonastes in Michigan Flora)

C. disperma


1. Culm angles smooth below inflorescence; rhizomes slender, 0.6–1.8 mm thick, shoots often arising 2–several in a cluster and many nodes without shoots; perigynium beaks 0.3–0.9 mm.

C. duriuscula

1. Culm angles at least slightly scabrous below inflorescence; rhizomes coarse, 1.8–3 mm thick, typically with long unbranched segments from which shoots arise singly every few nodes; perigynium beaks 0.7–1.2 mm.

C. praegracilis

CAREX SECT. GLAREOSAE (Heleonastes of Michigan Flora)

Carex loliacea is known from conifer swamps in several areas near Thunder Bay on the north shore of Lake Superior, and could occur in northern Michigan. The perigynia resemble those of C. tenuiflora, but with the spikes separated like those of C. disperma in sect. Dispermae.

1. Lowest bract bristle-like, several times as long as its spike; perigynia mostly 2.8–3.8 (–4) mm long, including very short smooth beak; spikes widely separated, containing 1–5 perigynia each.

2. Leaves 0.3–0.8 mm wide, filiform-involute.

C. billingsii

2. Leaves 0.8–1.9 mm wide, flat or somewhat M-folded.

C. trisperma

1. Lowest bract absent or at most about twice as long as its spike (if rarely prolonged, the perigynia smaller and often with serrulate beak); perigynia and spikes various.

3. Perigynia broadest near the base of the body, with a conspicuous beak 0.7–1.1 mm long; spikes mostly 7–15, usually ± overlapping or crowded into an ovoid to narrowly pyramidal head 2–4.5 cm long.

C. arcta

3. Perigynia broadest at or near the middle of the body; beak essentially absent or less than 0.6 mm long; spikes 2–8 (–10), at least the lower spikes well separated or, if crowded, the inflorescence only 0.6–2 cm long.

4. Spikes 2–4, crowded into a short inflorescence 0.6–2 cm long; perigynia 2.5–3.5 mm long, beak often smooth-margined.

5. Pistillate scales white-hyaline except for green center; perigynium beaks green to pale brown, the same color as the body.

C. tenuiflora

5. Pistillate scales reddish brown with a paler center; perigynium beaks reddish brown tinged with a hyaline apical rim, darker than the perigynium body.

C. heleonastes

4. Spikes 4–8 (–10), remote or ± crowded, but total inflorescence over 2 cm long; perigynia 1.7–2.6 mm long, beak usually minutely serrulate or scabrous.

6. Perigynia ca. 3–9 per spike (occasionally one or two spikes on a plant, especially terminal one, with as many as 15), loosely spreading, becoming rich brown in age; largest leaves ca. 1–2 mm wide; foliage and perigynia green when fresh.

C. brunnescens

6. Perigynia mostly 10–many per spike, appressed-ascending, greenish or dull brown in age; largest leaves (1.6–) 2–2.7 (–3.7) mm wide; foliage and perigynia glaucous or gray-green at least when fresh.

C. canescens


1. Staminate spike long-peduncled, elevated above summit of uppermost pistillate spikes; lowest pistillate spike usually on a separate basal peduncle; culms mostly solitary from elongate rhizomes; widest leaves 1.5–4 mm broad.

C. crawei

1. Staminate spike sessile or nearly so; lowest pistillate spike not on a basal peduncle; culms clumped, without elongate rhizomes; widest leaves 4.5–10 (–13) mm broad.

C. granularis

CAREX SECT. GRISEAE (Including Oligocarpae of Michigan Flora)

Carex glaucodea is known from northern Indiana and Ohio as well as southwestern Ontario and will likely be found in Michigan. It is like C. amphibola and C. grisea, but with glaucous leaves and more perigynia per spike (often 15–40) in contrast to usually fewer than 15 for C. grisea and C. amphibola.

1. Perigynia contracted to a distinct beak 0.5–1.3 mm long.

2. Leaf sheaths strongly hispidulous; perigynia ca. 4–5.5 mm long; plants brownish at base.

C. hitchcockiana

2. Leaf sheaths glabrous; perigynia ca. 3.5–4 mm long; plants reddish at base.

C. oligocarpa

1. Perigynia essentially beakless.

3. Peduncles of lateral spikes finely scabrous; staminate spike long-peduncled; perigynia 2.5–3.6 (–4) mm long, usually more than 20 per spike.

C. conoidea

3. Peduncles of lateral spikes smooth; staminate spike sessile or nearly so; perigynia 4–5 mm long, usually fewer than 15 per spike.

4. Perigynia ± orbicular in cross-section, mostly 1.8–2.3 times as long as wide and 2–2.6 mm wide.

C. grisea

4. Perigynia clearly obtusely triangular in cross-section, mostly 2.5–3.1 times as long as wide and 1.5–2.1 mm wide.

C. amphibola

CAREX SECT. HELEOGLOCHIN (Paniculatae of Michigan Flora)

Plants without red dots on the leaf sheaths and with longer anthers than in this group should be sought at couplet 21 of the key to sections.

1. Inflorescence 7.5–15 cm long; culms stout, 1.5–2.7 mm thick at about 3 cm below the inflorescence; broadest leaf blades 5–7 mm wide; perigynia deep olive-green at maturity, obovoid, very abruptly beaked; leaf sheaths concave at mouth; anthers ca. 1–1.2 mm long.

C. decomposita

1. Inflorescence 1.2–6.5 cm long (occasionally 9 cm in C. prairea); culms not over 1.5 mm thick at about 3 cm below inflorescence; broadest blades not over 3 mm wide; perigynia golden brown to deep brown (with green beak) at maturity (darker when over-ripe), lanceolate-ovate; leaf sheaths (when intact) ± prolonged ventrally at the mouth; anthers ca. 1.3–2.1 mm long.

2. Leaf sheaths whitish or pale ventrally except for purplish dots; inflorescence ± crowded, the lowermost spike (or branch) usually at least slightly overlapping the next above it (occasionally separated by a distance no more than its total length); perigynia tending to spread at maturity, therefore not concealed by the scales.

C. diandra

2. Leaf sheaths strongly tinged with copper color toward their summits ventrally; inflorescence ± interrupted, the lowermost spikes (or branches) often well separated or even peduncled; perigynia ± appressed at maturity, nearly or completely concealed by the large scales.

C. prairea

CAREX SECT. HIRTIFOLIAE (Triquetrae of Michigan Flora)

C. hirtifolia

CAREX SECT. HOLARRHENAE (Intermediae of Michigan Flora)

C. sartwellii

CAREX SECT. HYMENOCHLAENAE (Including Gracillimae, Sylvaticae, and Longirostres of Michigan Flora)

This section contains nearly all of the forest understory species with elongated, nodding pistillate spikes. This is a very variable assemblage, with some species, such as C. assiniboinensis, C. prasina, and C. sprengelii, appearing quite different from all the rest.

1. Terminal spike gynecandrous; sheaths ± softly pubescent or perigynia essentially beakless (except C. prasina).

2. Perigynia strongly angled, gradually tapering into a beak ca. 1–1.5 mm long; bract of lowest pistillate spike sheathless or with sheath up to 1.2 cm long; terminal spike mostly staminate, with at most a few perigynia at apex.

C. prasina (in part)

2. Perigynia obscurely angled or nearly terete, essentially beakless or beak less than 0.5 mm long; bract of lowest spike with sheath 1.5–8 cm or more in length; terminal spike staminate at base, pistillate toward apex.

3. Perigynia 1.3–1.6 mm wide, beakless; sheaths and blades glabrous.

C. gracillima

3. Perigynia 1.7–2.5 mm wide, abruptly contracted to a short beak; sheaths and leaf blades ± softly pubescent, at least below (sometimes very sparsely so).

4. Upper pistillate scales with a distinct prolonged awn greater than 0.5 mm long, often nearly equaling or exceeding the perigynia; lateral spikes entirely pistillate.

C. davisii

4. Upper pistillate scales merely acute (or at most with a tip less than 0.5 mm long), distinctly shorter than the perigynia; lateral spikes usually with a few staminate flowers at base.

C. formosa

1. Terminal spike staminate; sheaths glabrous (except C. castanea) and perigynia conspicuously beaked.

5. Perigynia pubescent.

C. assiniboinensis

5. Perigynia glabrous.

6. Leaf sheaths and blades (at least toward the base) ± hairy; pistillate spikes 1–2.5 cm long.

C. castanea

6. Leaf sheaths and blades glabrous (at most the lowermost bladeless sheaths minutely hispidulous); pistillate spikes mostly (2–) 2.5–6.5 cm long.

7. Basal sheaths reddish purple for at least several cm above the base; perigynia clearly nerved between the 2 ribs.

8. Perigynia short-stalked, the achene within sessile or nearly so; broadest leaves (5–) 6–10 (–12) mm wide; pistillate scales mostly awned or cuspidate.

C. arctata

8. Perigynia sessile but the achene within on a definite short stalk ca. 0.5–1 mm long; broadest leaves 2.5–4.5 (–5.5) mm wide; pistillate scales mostly not awned.

C. debilis

7. Basal sheaths brown, lacking any trace of reddish purple color (at most a small trace on the smaller sheaths in C. prasina); perigynia 2-ribbed, but otherwise nerveless or faintly nerved.

9. Perigynia (somewhat twisted) gradually tapering to a poorly defined conical beak, the cylindrical apical portion only 0.2–0.5 mm long.

C. prasina (in part)

9. Perigynia (symmetrical) tapering to abruptly contracted into a well developed cylindrical beak ca. 1.2–4.5 mm long.

10. Perigynia with ± spherical bodies; rhizomes horizontal, short creeping, and densely covered with bristle-like fibers.

C. sprengelii

10. Perigynia with more elongate, ellipsoid and obtusely trigonous bodies; rhizomes very short, sparsely and irregularly fibrous.

C. sylvatica


1. Sides of perigynia with at most 1 main nerve, otherwise nerveless or each with up to 6 obscure nerves; perigynium with a straightish or slightly bent short beak.

C. leptonervia

1. Sides of perigynia each with 7 or more conspicuous nerves of appoximately equal strength; perigynium with straightish or strongly bent beak.

2. Angles of bract sheaths smooth or nearly so (granular-papillose in C. ormostachya); beak of perigynium usually straight or short and slightly bent.

3. Perigynia mostly more than twice as long as wide, tapered to the straightish beak; basal sheaths brown.

C. laxiflora

3. Perigynia mostly twice as long as wide, or shorter, abruptly contracted to a very short bent beak; basal sheaths with some red-purple tinting.

C. ormostachya

2. Angles of bract sheaths minutely ciliate-serrulate; beak of perigynium strongly bent.

4. Widest leaves 8 mm or more broad; pistillate scales broadly obtuse or truncate, at most scarcely toothed at apex; staminate spike sessile or nearly so.

C. albursina

4. Widest leaves often less than 8 mm broad; pistillate scales acuminate, awned, or cuspidate; staminate spike sessile or peduncled.

5. Staminate spike sessile or at most short-peduncled, exceeded by one or more of the bracts; upper pistillate spikes ± crowded; scales not (or only slightly) flushed with orange-brown; bases of plants not red tinged.

C. blanda

5. Staminate spike peduncled, elevated above pistillate spikes and (usually) ends of the bracts; pistillate spikes scattered; staminate and sometimes pistillate scales often strongly flushed with orange-brown; bases of plants red tinged, at least on a few bladeless basal sheaths.

C. gracilescens

CAREX SECT. LEPTOCEPHALAE (Polytrichoideae of Michigan Flora)

C. leptalea

CAREX SECT. LEUCOGLOCHIN (Orthocerates of Michigan Flora)

C. pauciflora


Species of this section have roots with a distinctive yellowish or orange felting of root hairs, which allows them to be readily identified vegetatively.

1. Pistillate scales nearly or quite as broad as the perigynia and often only slightly if at all longer; staminate spike (12–) 15–30 (–50) mm long; plants strongly stoloniferous.

C. limosa

1. Pistillate scales distinctly narrower than perigynia, generally with narrowly acuminate tips much exceeding them; staminate spike 5–12 (–15) mm long; plants loosely clumped.

C. magellanica


1. Pistillate spikes spherical or nearly so, scarcely if at all longer than wide; sheath of uppermost leaf absent or less than 1.5 (–2.5) cm; style straight or sinuous or contorted (especially in C. intumescens) just below or at the middle; beak of perigynium much shorter than the body.

2. Perigynia (7–) 10–31 per spike, radiating in all directions, narrowed at the base to a ± broad cuneate stalk, sometimes hispidulous basally; pistillate spikes 1–2 (–3).

C. grayi

2. Perigynia 2–8 (–12) per spike, mostly spreading-ascending, rounded at the base, glabrous (and often very shiny); pistillate spikes (1–) 2–5.

C. intumescens

1. Pistillate spikes cylindrical or short-oblong, usually definitely longer than broad; sheath of uppermost leaf usually 1.7 cm or longer; style strongly bent and contorted immediately above the body of the achene; beak of perigynium nearly or quite as long as the body.

3. Body of achene with broadly diamond-shaped sides, mostly 2.4–3.4 mm wide, at most 0.5 mm longer than wide, the angles each with a prominent swollen knob.

C. lupuliformis

3. Body of achene with somewhat diamond-shaped to ± elliptic or ovate sides, 1.7–2.6 (–2.8) mm wide, usually 1 mm or more longer than wide, the angles obscurely if at all knobbed.

C. lupulina


1. Perigynium abruptly contracted into a beak mostly 0.25–0.5 times as long as body; larger perigynia 1.5–2.3 mm wide with broadly ovate to ± orbicular bodies, fully mature (orange-brown) mid-June to mid-July.

C. annectens

1. Perigynium tapering or contracted into a beak 0.5–1 times as long as body; larger perigynia 1.1–1.9 mm wide with ovate bodies, fully mature (greenish to dull yellow or brown) mid-July to mid-August (in southern Michigan).

C. vulpinoidea


1. Perigynia pubescent.

2. Perigynia 4.5–6.5 mm long, sparsely hairy, the strong nerves of perigynium and even cellular detail of body therefore evident; plants usually of dry and sandy habitats.

C. houghtoniana

2. Perigynia 3–4.5 (–5.2) mm long, densely pubescent, nerving of perigynium and cellular detail therefore obscured; plants usually of wetlands.

3. Leaf blades involute to triangular-channeled, 0.7–2 (–2.2) mm wide, those of vegetative shoots especially long-prolonged into a curled, filiform tip; leaves and lowermost bracts with the midvein low, rounded, and forming an inconspicuous keel (at least proximally).

C. lasiocarpa

3. Leaf blades flat or folded into an M-shape except at the base and near the tip, (2–) 2.2–4.5 (–6.5) mm wide, not prolonged into a long filiform tip; leaves and lowest bract with the midvein forming a prominent and sharply pointed keel for much of the length.

C. pellita

1. Perigynia glabrous.

4. Perigynia 3–4.5 mm long.

C. acutiformis

4. Perigynia 4.8–7.5 mm long.

5. Longest ligules 13–40 (–56) mm long, much longer than wide; culms lateral, with reddish bladeless basal sheaths; perigynia usually strongly many-nerved.

C. lacustris

5. Longest ligules 2–10 (–12) mm long, less than twice as long as wide; culms central, with persistent dead brownish remains of previous years leaves at base; perigynia nerveless or delicately nerved.

C. hyalinolepis


If forms of Carex flacca with glabrous perigynia are found in Michigan, they may key here, but can be distinguished by their usually darker purple colored pistillate and staminate scales and most culms having 2–3 staminate spikes.

1. Perigynium with a beak ca. 1 mm long.

C. vaginata

1. Perigynium beakless, indistinctly beaked, or contracted to beak less than 0.5 mm.

2. Perigynia strongly ascending, beakless or cuneately tapering to an essentially erect, very short straight beak; leaves stiff, thick, channeled, strongly glaucous.

C. livida

2. Perigynia ascending to spreading, concavely tapering (at least on one side) to a bent apex; leaves relatively thin and flexible, flat or folded, green to somewhat glaucous.

3. Bladeless basal sheaths and proximal leaf sheaths strongly tinged with reddish purple; plants forming loose clumps to extensive closed colonies of vegetative shoots from superficial rhizomes; perigynia ± 2-ranked; plants of rich forests.

C. woodii

3. Bladeless basal sheaths and proximal leaf sheaths brownish, green, or faintly, irregularly tinged with reddish purple; plants usually with vegetative shoots widely scattered and inconspicuous from deep, difficult to collect rhizomes; perigynia 3–6-ranked; plants of moist, usually sunny habitats.

4. Largest achenes 1.7–2.2 (–2.5) mm wide; longest anthers (3.5–) 4–4.6 mm long; ligules mostly 0.4–1.2 times as long as wide.

C. meadii

4. Largest achenes 1.2–1.7 (–1.8) mm wide; longest anthers 2.8–3.5 (–3.8) mm long; ligules mostly (0.8–) 1–2 times as long as wide.

C. tetanica

CAREX SECT. PHACOCYSTIS (Acutae and Cryptocarpae of Michigan Flora)

The species of this section can be difficult to distinguish from each other without complete basal parts.

1. Pistillate spikes on ± lax peduncles, at length drooping, the scales prominently awned; body of achene with an irregular notch, constriction, or wrinkle on one side.

2. Sheaths smooth; bodies of most if not all pistillate scales shallowly lobed at summit (on each side of base of the awn).

C. crinita

2. Sheaths scabrous-hispidulous; bodies of most or all pistillate scales on lower part of spike truncate or tapered at summit.

C. gynandra

1. Pistillate spikes erect or strongly ascending, often sessile, the scales acute or acuminate, not awned; body of achene smooth and ± regular.

3. Fertile culms of current year with conspicuous bladeless sheaths at base, not surrounded by dried-up bases of the previous year’s leaves but arising laterally; lowest bract usually shorter than to approximately equaling the inflorescence.

4. Perigynia suborbicular to obovoid, 2–2.3 mm long at maturity, broadest at or slightly above middle, rather abruptly contracted to a minute apiculus, at least the lower ones in a spike much exceeded by the spreading scales; lower leaf sheaths not or only slightly tearing to form a ladder like arrangement of fibers, the intact sheaths smooth ventrally; ligule longer than width of leaf blade; plants with short, ascending rhizomes.

C. haydenii

4. Perigynia elliptic to ovate, mostly 2.2–2.7 (–3.3) mm long at maturity, broadest at or slightly below the middle, ± tapered to apex, as long as or longer than the scales (rarely exceeded by scales); ventral surface of lower leaf sheaths tearing to form a ladder-like arrangement of fibers (ladder-fibrillose) or if not, then the ligule shorter than width of leaf blade; plants with long horizontal rhizomes.

5. Ligule longer than width of leaf blade (deeply inverted V-shaped); ventral surface of lower leaf sheaths tearing to form a ladder-like arrangement of fibers and usually minutely scabrous and red-dotted, especially near the apex.

C. stricta

5. Ligule shorter than width of leaf blade (often nearly horizontal); ventral surface of lower leaf sheaths not tearing to form a ladder like arrangement of fibers, smooth and whitish.

C. emoryi

3. Fertile culms of current year mostly lacking bladeless sheaths at base, arising centrally from tufts of dried-up bases of previous years leaves; lowest bract usually conspicuously longer than the inflorescence (except in C. nigra).

6. Perigynia essentially nerveless, except sometimes at the base only; staminate spikes usually 2 or more.

C. aquatilis

6. Perigynia conspicuously few-ribbed on both sides; staminate spike usually 1.

7. Plants densely tufted, without long rhizomes; scales with a broad central green portion about as wide as the darker margins; leaves mostly overtopping spikes.

C. lenticularis

7. Plants colonial from elongated rhizomes; scales with very narrow green portion much narrower than the broad, dark margins, scarcely if at all broader than the midrib; leaves mostly shorter than summit of culm.

C. nigra

CAREX SECT. PHAESTOGLOCHIN (Bracteosae of Michigan Flora)

These are common, mostly upland species of forests and open habitats, including a number of ruderal or even weedy species, some of which are among our few non-native species of Carex. Carex divulsa Stokes, a large Eurasian species is rare in southern Ontario and northern Ohio and may be found in Michigan. It resembles C. spicata, but with a longer inflorescence with the lowest spikes clearly separated and no purple tinting in the roots.

1. Leaf sheaths loose, white with green veins or mottled green and white on back; wider blades (4.3–) 5–10 mm broad (or rarely only 3 mm in C. gravida and C. aggregata with very slender elongate stigmas).

2. Pistillate scales with narrowly acuminate or awned tips reaching over the bases or all the way to the ends of the beaks of the perigynia they subtend; anthers ca. 1.1–2.4 mm long; stigmas quite elongate and slender, when intact and well developed, protruding 1.5 mm or more from the perigynia; spikes crowded in a dense inflorescence.

3. Ventral surface of leaf sheath strongly concave and thickened at the summit, usually intact on specimens; face of mature perigynia green at maturity.

C. aggregata

3. Ventral surface of leaf sheaths thin or slightly thickened at the summit, easily broken; face (over achene) of mature perigynia mostly yellow-brown.

C. gravida

2. Pistillate scales with short-acuminate, slightly cuspidate, acute, or obtuse tips almost or not at all reaching the bases of the beaks of the perigynia they subtend; anthers 0.7–1.1 (–1.3) mm long; stigmas shorter and stouter, protruding slightly from perigynia; spikes crowded or the lower (in C. sparganioides) becoming well separated.

4. Spikes close together, the lower not separated more than their length, usually ± overlapping; perigynia (3.2–) 3.6–4.5 mm long, (1.7–) 2–3 times as long as wide, the bodies not wing-margined; widest leaf blades (4.3–) 5–7 (–8) mm broad.

C. cephaloidea

4. Spikes well separated below, the lower ones ± remote; perigynia 3–4.1 mm long, 1.3–1.8 (–2) times as long as wide, the bodies ± narrowly thin-winged; widest leaf blades 5.5–10 mm broad.

C. sparganioides

1. Leaf sheaths ± tight and slender and uniform green or whitish on back (or sometimes mottled in the slender and narrow-leaved C. leavenworthii); wider blades 0.9–4.3 (–4.5) mm broad.

5. Pistillate scales with the sides brown or purple, acuminate-awned; larger perigynia mostly 3.5–5.5 mm long.

6. Ligules 2–4 mm long, as wide as or wider than long; larger roots brownish internally.

C. muricata

6. Ligules 4–8 mm long, distinctly longer than wide; larger roots purple internally.

C. spicata

5. Pistillate scales whitish or greenish, obtuse to acuminate; larger perigynia 2.6–4.1 mm long.

7. Perigynia mostly widely spreading at maturity, conspicuously spongy-thickened at their bases and there puckered in drying, the wire-like margin above the base tending to turn inward.

8. Beak of perigynium smooth, only slightly exceeding the tip of the acuminate scale; inflorescences with spikes rather close together or crowded.

9. Spongy-thickened zone of mature perigynium 1.2–1.9 mm long, 0.4–0.6 times as long as the perigynium; perigynia 1.3–1.8 mm wide.

C. retroflexa

9. Spongy-thickened zone of mature perigynium 0.9–1.2 mm long, 0.25–0.4 times as long as the perigynium; perigynia 1–1.3 mm wide.

C. texensis

8. Beak of perigynium minutely serrulate, much exceeding the tip of the acute to obtuse or rounded scale; inflorescence interrupted, with ± separated spikes.

10. Wider leaf blades mostly 0.9–1.9 mm broad; stigmas reddish to dark brown, slender and elongate (when intact), often protruding 1–1.5 mm or more, often reflexed but otherwise straight or slightly sinuous.

C. radiata

10. Wider leaf blades mostly (1.5–) 1.7–2.7 mm broad; stigmas very dark reddish brown, comparatively short and stout, strongly curled.

C. rosea

7. Perigynia mostly ascending and not widely spreading, at most with thin spongy area at base not conspicuously puckered in drying (unless immature), the margin above flat or slightly incurved.

11. Inflorescence crowded to oblong and interrupted (the lower spikes overlapping but distinct); leaf blades densely papillose above [20×–30×]; bodies of scales more (often much more) than half as long as bodies of the perigynia they subtend; larger perigynia in spike 3–4.1 mm long, (1.8–) 2–2.6 mm wide.

12. Perigynia with at most a few very slender faint nerves on dorsal face; anthers 1.1–1.5 mm long; inflorescence always very densely crowded, ovoid.

C. mesochorea

12. Perigynia with several thick (though sometimes rather faint) nerves on dorsal face; anthers 1.5–2.3 mm long; inflorescences crowded to elongate-oblong.

C. muehlenbergii

11. Inflorescence densely crowded, ± ovoid, the spikes in a close head and nearly indistinguishable except by the slightly protruding setaceous bracts; leaf blades smooth above the collar or the cellular outlines conspicuous, but only rarely some leaves papillose; bodies of scales usually about or only slightly more than half as long as bodies of the perigynia; perigynia 2.5–3.2 (very rarely 3.5) mm long, 1.5–1.8 (–2) mm wide.

13. Perigynia broadest at or near the middle of the orbicular to broadly elliptic body, the perigynium wall tightly wrapping the achene near the base, without any spongy tissue inside the perigynia; anthers 0.7–1 (–1.3) mm long; beak of perigynium uniformly strongly serrulate.

C. cephalophora

13. Perigynia broadest toward the base of the very broadly ovoid body, whitish, spongy (styrofoam-like) tissue present between the achene and perigynium wall at the base; anthers (0.6–) 0.8–1.7 mm long; beak of perigynium usually smooth or sparsely serrulate, rarely more strongly serrulate.

C. leavenworthii


1. Pistillate scales much wider than the perigynia, embracing and nearly concealing them; staminate scales about 3 (usually hidden by upper perigynia); wider leaf blades (3–) 3.5–5.5 mm broad; anthers ca. 1.3–1.6 mm long.

C. backii

1. Pistillate scales mostly narrower than the perigynia, not concealing them; staminate scales about 4 or more; wider leaf blades 2–2.6 (–3.5) mm broad; anthers ca. 0.5–1.1 mm long.

C. jamesii

CAREX SECT. PHYSOGLOCHIN (Dioicae of Michigan Flora)

C. gynocrates

CAREX SECT. POROCYSTIS (Virescentes of Michigan Flora)

1. Perigynia pubescent; terminal spike pistillate at apex, staminate at base.

2. Pistillate spikes ellipsoid or thick-cylindric, the lower ones (0.5–) 0.7–1.5 (–2) cm long; anthers 0.7–1.3 (–1.6) mm long; culms often shorter than the leaves.

C. swanii

2. Pistillate spikes linear-cylindric, the lower ones 1.8–3.5 cm long; anthers 1.5–2.5 mm long; culms usually surpassing the leaves.

C. virescens

1. Perigynia glabrous; terminal spike staminate or pistillate at apex.

3. Terminal spike entirely staminate; perigynia ellipsoid-cylindric, rather faintly nerved.

C. pallescens

3. Terminal spike pistillate at apex; perigynia obovoid-orbicular, ± compressed, strongly nerved (especially on dorsal face).

4. Pistillate scales longer than the perigynia, with an awn 0.5–2 mm long.

C. bushii

4. Pistillate scales shorter than the perigynia, awnless, or with an awn not more than 0.5 mm long.

C. hirsutella

CAREX SECT. RACEMOSAE (Atratae of Michigan Flora)

The distinctive Carex shortiana (Section Shortianae) is known from southern Ontario and northern Ohio, and likely will be found in Michigan. It would key here, but differs from all our members of Section Racemosae in having a few staminate flowers at the base of all lateral spikes.

1. Pistillate scales mostly awned or narrowly acuminate, exceeding the perigynia; ventral surface of lower leaf sheaths tearing into fibers; throughout the state.

C. buxbaumii

1. Pistillate scales obtuse or acute, equaling or shorter than the perigynia; ventral surface of lower sheaths not tearing to form fibers; rare species of Lake Superior region.

2. Pistillate spikes peduncled, usually spreading or drooping; anthers ca. 1.5–2.5 mm long.

C. atratiformis

2. Pistillate spikes ± sessile and erect, rather crowded; anthers ca. 1 (–1.2) mm or less long.

C. media

CAREX SECT. ROSTRALES (Folliculatae of Michigan Flora)

1. Broadest leaf blades 5–17 mm wide; sheaths of bracts with a ± prolonged lobe at mouth; staminate spike usually peduncled, its tip projecting well above the pistillate spikes.

C. folliculata

1. Broadest leaf blades 1.5–3.5 mm wide; sheaths of bracts concave at mouth; staminate spike sessile or very short-peduncled, scarcely if at all projecting above the pistillate spikes.

C. michauxiana


C. scirpoidea


1. Pistillate scales with a long awn exceeding the beak of the perigynium; achenes ca. 1.5 mm long.

C. frankii

1. Pistillate scales awnless or short-awned, much shorter than the beak, usually ± hidden among the dense perigynia; achenes ca. 2.2–3 mm long.

2. Achenes slenderly ellipsoid, slightly more than twice as long as wide, terminated by a strongly sinuous style; pistillate scales very sharp-tipped or short-awned.

C. squarrosa

2. Achenes broadly ellipsoid, about or slightly less than twice as long as wide, terminated by a ± straight style; pistillate scales ± acute in outline but blunt at the very tip.

C. typhina


The distinctions between species in this section are subtle; however, the species have particular (though not always easy to describe) habitat preferences that help with field identifications. When selecting perigynia for examination, select from the lowest 2–3 perigynia in the spike; upper perigynia of spikes tend to converge on approximately the same shape in all species.

1. Spikes solitary; leaves involute; anthers 2–3.6 mm.

C. exilis

1. Spikes 2–8; leaves flat or plicate; anthers 0.6–2.2 (–2.3) mm.

2. Perigynium beak smooth-margined.

C. seorsa

2. Perigynium beak at least sparsely serrulate on margins.

3. Widest leaves 2.8–5 mm wide.

C. wiegandii

3. Widest leaves 0.8–2.7 mm wide.

4. Terminal spikes entirely staminate.

C. sterilis (in part)

4. Terminal spikes partly or wholly pistillate.

5. Terminal spikes without a distinct clavate base of staminate scales, staminate portion less than 1 mm long; anthers (1–) 1.2–2.2 (–2.3) mm long.

C. sterilis (in part)

5. Terminal spikes with a distinct clavate base of staminate scales 1–8 (–16.5) mm long; anthers 0.6–1.6 (–2) mm long.

6. Lower perigynia in the spikes 2–3 mm wide.

C. atlantica (in part)

6. Lower perigynia in the spikes 0.9–1.9 mm wide.

7. Lower perigynia mostly 2.9–3.6 (–4) mm long, (1.7–) 1.8–3.6 times as long as wide; beaks 0.9–2 mm long, mostly 0.5–0.8 times as long as the body.

C. echinata

7. Lower perigynia mostly 1.9–3 mm long, 1–2 (–2.2) times as long as wide; beaks 0.4–0.9 mm long, mostly 0.2–0.5 times as long as body.

8. Perigynia mostly nerveless over achene on ventral surface; perigynium beaks conspicuously setulose-serrulate; perigynia often ± convexly tapered from widest point to beak, forming a “shoulder.”

C. interior

8. Perigynia 1–10-nerved over achene on ventral surface; perigynium beaks more sparsely serrulate with definite spaces between the often single teeth; perigynia cuneately or even concavely tapered from widest point to beak.

C. atlantica (in part)

CAREX SECT. THURINGIACA (Pendulinae of Michigan Flora)

C. flacca

CAREX SECT. VESICARIAE (Including Pseudocypereae of Michigan Flora)

1. Pistillate scales with a prominent, scabrous awn; often the body also ciliate.

2. Perigynia ± reflexed at maturity, hard-walled, uninflated, flattened-triangular in cross-section, strongly and closely nerved with most nerves separated by less than three times their width; longest beak teeth 0.7–2.2 mm long.

3. Spikes 12–18 mm thick; beak teeth strongly outcurved, the longest 1.3–2.1 (–2.8) mm long.

C. comosa

3. Spikes 9–12 mm thick; beak teeth straight or slightly outcurved, the longest 0.7–1.2 (–1.3) mm long.

C. pseudocyperus

2. Perigynia spreading to ascending, thin-textured, ± inflated, ± round in cross-section; many nerves separated by more than three times their width; longest beak teeth 0.3–0.7 (–0.9) mm long.

4. Staminate scales (except sometimes the lowermost) acute to acuminate, essentially smooth-margined except at the very tip; plants extensively colonial from elongate, creeping rhizomes; perigynia 7–11-nerved.

C. schweinitzii

4. Staminate scales (at least some) with a distinct, scabrous awn and sometimes also ciliate-margined; plants densely to loosely cespitose, rhizomes connecting individual culms in a clump not more than ca. 10 cm long; perigynia 7–25-nerved.

5. Perigynia 15–20-nerved, the nerves (except for the two prominent laterals) fusing together and becoming indistinguishable from about the middle of the beak to the apex, bodies ellipsoid, 1.4–2.2 mm wide; achenes smooth.

C. hystericina

5. Perigynia 7–12-nerved, the nerves separate nearly to the beak apex, the bodies broadly ellipsoid to ± spherical, (1.8–) 2–3.5 mm wide; achenes rough-papillate.

C. lurida

1. Pistillate scales smooth-margined, obtuse to acuminate, awnless (rarely the lowermost awned in C. rostrata and C. utriculata).

6. Leaf blades and bracts involute-filiform, wiry, 1–3 mm wide; stems round or obtusely trigonous in cross-section, smooth; pistillate spikes 3–15 (–18)-flowered, nearly spherical or short-oblong (not over 2 cm long); staminate spike usually solitary.

C. oligosperma

6. Leaf blades and bracts flat, U-, V-, or W-shaped in cross-section, 1.5–12 (–15) mm wide; stems round to trigonous, often scabrous-angled; pistillate spikes usually more than 15-flowered, oblong to long-cylindric; staminate spikes normally 2 or more (often 1 in C. retrorsa).

7. Perigynia (4–) 4.5–7 mm thick; achenes with a deep notch or constriction on one angle.

C. tuckermanii

7. Perigynia 2.5–3.5 (–4) mm thick; achenes symmetrical, not notched on one angle.

8. Lowest pistillate bract (2.5–) 3–9 times as long as the entire inflorescence; mature perigynia 7–12 mm long, at least the lower reflexed or widely spreading; staminate spike often 1, its base (or base of lowest staminate spike if more than 1) slightly if at all elevated above summit of the crowded pistillate spikes (rarely lower spike remote).

C. retrorsa

8. Lowest pistillate bract less than 3 times as long as inflorescence; perigynia (4–) 4.5–7.5 (very rarely 8.5) mm long, ascending or spreading; staminate spikes mostly 2–4, generally well elevated above the pistillate spikes.

9. Leaves strongly papillose on upper surface, U-shaped in cross-section, glaucous, widest leaves 1.5–4.5 (–7.5) mm wide; stems round or very obtusely triangular, smooth below inflorescence.

C. rostrata

9. Leaves smooth or scabrous on upper surface, flat or folded, pale to dark green, widest leaves 3–12 (–15) mm wide; stems triangular, often scabrous below the inflorescence.

10. Colonial from long-creeping rhizomes; widest leaves (4.5–) 5–12 (–15) mm wide; ligules about as long as wide; basal sheaths usually spongy-thickened with little or no red tingeing; perigynia (at least those on lower portion of fully mature spike) ± widely spreading; stems bluntly triangular and sparsely and irregularly scabrous below the inflorescence.

C. utriculata

10. Cespitose; widest leaves 3–5 (–6) mm wide; ligules longer than wide; basal sheaths not spongy-thickened and often tinged with reddish purple; perigynia ascending; stems sharply triangular and scabrous-angled below the inflorescence.

C. vesicaria


1. Perigynia 6.5–8 mm long, enlarged below with a spongy disc-like area much broader than the rest of the body; beak twice as long as body of perigynium, or longer; thin ventral surface of leaf sheaths with copious tiny purplish dots.

C. crus-corvi

1. Perigynia (2.6–) 3–6.2 mm long, corky below but without so distinct a disc-like area; beak slightly longer than the body of perigynium, or shorter; thin ventral surface of leaf sheaths dotted or not.

2. Perigynia somewhat contracted or ± cuneately tapered into the beak (this then difficult to define, but about equaling or slightly exceeding the body, if the latter is measured from the base of perigynium to summit of achene), 4–6.2 mm long, with at least a few nerves ventrally; ventral surface of leaf sheaths not dotted with purplish.

3. Sheaths thickened (or even ± cartilaginous) at the concave or truncate mouth, smooth and unwrinkled ventrally; perigynia 4.7–6.2 mm long.

C. laevivaginata

3. Sheaths thin (usually broken) at the prolonged (when intact) mouth, rather strongly puckered or cross-wrinkled ventrally, very rarely nearly or quite smooth; perigynia 4–5 (–5.5) mm long.

C. stipata

2. Perigynia contracted into a beak no longer than the body, (2.6–) 3–4.5 (–4.8) mm long, essentially nerveless ventrally; ventral surface of leaf sheaths sparsely to strongly dotted with purplish, especially toward the apex.

4. Sheath fronts not cross-wrinkled ventrally; achenes about as long as wide; perigynia nerveless or with 3–5 very faint veins dorsally.

C. alopecoidea

4. Sheath fronts clearly cross-wrinkled ventrally, at least near the apex; achenes distinctly longer than wide; perigynia with 3–5 prominent veins dorsally.

C. conjuncta

All species found in Carex

Carex acutiformisSEDGE 
Carex adustaSEDGE 
Carex aggregataSEDGE 
Carex alataWINGED SEDGE 
Carex albicansSEDGE 
Carex albolutescensGREENISH-WHITE SEDGE 
Carex albursinaSEDGE 
Carex alopecoideaSEDGE 
Carex amphibolaSEDGE 
Carex annectensSEDGE 
Carex aquatilisSEDGE 
Carex arctaSEDGE 
Carex arctataSEDGE 
Carex argyranthaSEDGE 
Carex assiniboinensisASSINIBOIA SEDGE 
Carex atherodesSEDGE 
Carex atlanticaSEDGE 
Carex atratiformisSEDGE 
Carex aureaSEDGE 
Carex backiiSEDGE 
Carex bebbiiSEDGE 
Carex bicknelliiSEDGE 
Carex billingsiiSEDGE 
Carex blandaSEDGE 
Carex breviorSEDGE 
Carex bromoidesSEDGE 
Carex brunnescensSEDGE 
Carex bushiiBUSH'S SEDGE 
Carex buxbaumiiSEDGE 
Carex canescensSEDGE 
Carex capillarisSEDGE 
Carex careyanaSEDGE 
Carex castaneaSEDGE 
Carex cephaloideaSEDGE 
Carex cephalophoraSEDGE 
Carex chordorrhizaSEDGE 
Carex communisSEDGE 
Carex comosaSEDGE 
Carex concinnaBEAUTY SEDGE 
Carex conjunctaSEDGE 
Carex conoideaBEAUTY SEDGE 
Carex craweiSEDGE 
Carex crawfordiiSEDGE 
Carex crinitaSEDGE 
Carex cristatellaSEDGE 
Carex crus-corviSEDGE 
Carex cryptolepisSEDGE 
Carex cumulataSEDGE 
Carex davisiiDAVIS' SEDGE 
Carex debilisSWAMP SEDGE 
Carex decompositaLOG SEDGE 
Carex deflexaSEDGE 
Carex deweyanaSEDGE 
Carex diandraSEDGE 
Carex digitalisSEDGE 
Carex dispermaSEDGE 
Carex duriusculaSEDGE 
Carex eburneaSEDGE 
Carex echinataSEDGE 
Carex echinodesSEDGE 
Carex emoryiSEDGE 
Carex exilisSEDGE 
Carex festucaceaFESCUE SEDGE 
Carex flaccaSEDGE 
Carex flavaSEDGE 
Carex foeneaSEDGE 
Carex folliculataSEDGE 
Carex formosaSEDGE 
Carex frankiiFRANK'S SEDGE 
Carex garberiSEDGE 
Carex gracilescensSEDGE 
Carex gracillimaSEDGE 
Carex granularisSEDGE 
Carex gravidaSEDGE 
Carex grayiSEDGE 
Carex griseaSEDGE 
Carex gynandraSEDGE 
Carex gynocratesSEDGE 
Carex haydeniiHAYDEN'S SEDGE 
Carex heleonastesSEDGE 
Carex hirsutellaSEDGE 
Carex hirtaSEDGE 
Carex hirtifoliaSEDGE 
Carex hitchcockianaSEDGE 
Carex houghtonianaSEDGE 
Carex hyalinolepisSEDGE 
Carex hystericinaSEDGE 
Carex inopsSEDGE 
Carex interiorSEDGE 
Carex intumescensSEDGE 
Carex jamesiiJAMES' SEDGE 
Carex lacustrisSEDGE 
Carex laevivaginataSEDGE 
Carex lasiocarpaSEDGE 
Carex laxiculmisSEDGE 
Carex laxifloraSEDGE 
Carex leavenworthiiSEDGE 
Carex lenticularisSEDGE 
Carex leptaleaSEDGE 
Carex leptonerviaSEDGE 
Carex limosaBOG SEDGE 
Carex lividaSEDGE 
Carex longiiSEDGE 
Carex lucorumSEDGE 
Carex lupuliformisSEDGE 
Carex lupulinaSEDGE 
Carex luridaSEDGE 
Carex magellanicaSEDGE 
Carex meadiiSEDGE 
Carex mediaSEDGE 
Carex merritt-fernaldiiSEDGE 
Carex mesochoreaSEDGE 
Carex michauxianaSEDGE 
Carex molestaSEDGE 
Carex muehlenbergiiSEDGE 
Carex muricataSEDGE 
Carex muskingumensisSEDGE 
Carex nigraBLACK SEDGE 
Carex normalisSEDGE 
Carex novae-angliaeNEW ENGLAND SEDGE 
Carex oligocarpaSEDGE 
Carex oligospermaSEDGE 
Carex ormostachyaSEDGE 
Carex pallescensPALE SEDGE 
Carex paucifloraSEDGE 
Carex peckiiSEDGE 
Carex pedunculataSEDGE 
Carex pellitaSEDGE 
Carex pensylvanicaSEDGE 
Carex plantagineaSEDGE 
Carex platyphyllaBROAD-LEAVED SEDGE 
Carex praegracilisSEDGE 
Carex praireaSEDGE 
Carex prasinaSEDGE 
Carex praticolaSEDGE 
Carex projectaSEDGE 
Carex pseudocyperusSEDGE 
Carex retroflexaSEDGE 
Carex retrorsaSEDGE 
Carex richardsoniiRICHARDSON'S SEDGE 
Carex rossiiROSS' SEDGE 
Carex rostrataSEDGE 
Carex sartwelliiSEDGE 
Carex scabrataSEDGE 
Carex schweinitziiSEDGE 
Carex scirpoideaBULRUSH SEDGE 
Carex scopariaSEDGE 
Carex seorsaSEDGE 
Carex siccataSEDGE 
Carex sparganioidesSEDGE 
Carex spicataSEDGE 
Carex sprengeliiSEDGE 
Carex squarrosaSEDGE 
Carex sterilisSEDGE 
Carex stipataSEDGE 
Carex stramineaSTRAW SEDGE 
Carex strictaSEDGE 
Carex suberectaSEDGE 
Carex swaniiSEDGE 
Carex sychnocephalaLONG-BEAKED SEDGE 
Carex sylvaticaSEDGE 
Carex teneraSEDGE 
Carex tenuifloraSEDGE 
Carex tetanicaSEDGE 
Carex texensisSEDGE 
Carex tinctaSEDGE 
Carex tonsaSEDGE 
Carex tribuloidesSEDGE 
Carex trichocarpaHAIRY-FRUITED SEDGE 
Carex trispermaSEDGE 
Carex tuckermaniiSEDGE 
Carex typhinaCAT-TAIL SEDGE 
Carex umbellataSEDGE 
Carex utriculataSEDGE 
Carex vaginataSEDGE 
Carex vesicariaSEDGE 
Carex virescensSEDGE 
Carex viridistellataSEDGE 
Carex viridulaSEDGE 
Carex vulpinoideaSEDGE 
Carex wiegandiiWIEGAND'S SEDGE 
Carex woodiiSEDGE 


MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. December 2, 2022. https://michiganflora.net/genus.aspx?id=Carex.