Home ยป Juncaceae

Juncus

Specimens with well-developed fruit and seeds are necessary for accurate identification in some species complexes. Filaments at least are persistent even on older flowers and may be seen under the perianth parts. Flowers occasionally are reduced to bulblets or, in species with the leaf blades terete with hard cross-partitions at regular intervals, are replaced by striking, enlarged insect galls.

1. Inflorescence apparently lateral, one conspicuous terete involucral bract appearing to be a straight continuation of the stem, exceeding the inflorescence, which thus looks as if bursting from the side of the stem; stem leaves without blades, reduced to basal sheaths.

2. Stamens 3, the anthers about equaling the length of the filaments or slightly shorter; stems in dense clumps.

3. Stems with ca. 30–60 fine ridges just below inflorescence, appearing nearly smooth when fresh; when dry, the ridges closely spaced, rarely separated by more than twice their width; ridge tops [30×] ± flat and not notably more shiny than the rest of the stem.

J. effusus

3. Stems with ca. 10–25 ridges just below inflorescence, clearly textured even when fresh; the ridges, when dry, separated by up to ca. 4–5 times or more the width of the ridge; ridge tops shiny with low papillae [30×].

J. pylaei

2. Stamens 6, the anthers various; stems spaced along the rhizome singly or in small tufts (densely clumped only in the rare, glaucous J. inflexus).

4. Inflorescence up to 2 cm long; sepals green or pale brown (when old); anthers about half as long as filaments or shorter; rhizome slender, less than 2 mm in diameter; involucral bract usually more than half as long as the stem below (sometimes even longer, the inflorescence then appearing to be on lower half of the plant); sheaths pale brown.

J. filiformis

4. Inflorescence over 2 cm long, or if shorter, the sepals deep brown; anthers about as long as the filaments or longer; rhizome stout (even woody), (3–) 4 mm or more in diameter; involucral bract (with rare individual exceptions in a population) less than half as long as the stem below the inflorescence; sheaths pale or more often deep brown or maroon.

5. Stems prominently ridged, glaucous, densely clumped; anthers about the length of the filaments; sepals largely green or dull brown when old.

J. inflexus

5. Stems smooth, neither ridged nor glaucous, arising singly or in small tufts from the rhizome; anthers at least twice as long as the filaments; sepals marked with deep brown.

J. balticus

1. Inflorescence terminal, no involucral bract appearing to be a straight continuation of the stem; at least some sheaths bearing leaf blades.

6. Leaf blades flat, involute, or terete, but without hard cross-partitions.

7. Leaf blades terete, at least toward the end (sometimes firmly rounded but with a shallow or deep channel basally).

8. Inflorescence usually a fourth or more the height of the plant; adjacent flowers (single or groups of 2) separated on the ± one-sided, recurving branches of the inflorescence by a distance (at least when mature) distinctly greater than the length of the flowers; some or all flowers often converted to bulblets.

J. pelocarpus (in part)

8. Inflorescence much less than 1/4 the height of the plant, compact, with ± crowded flowers.

9. Inflorescence 1–4 (–5)-flowered; seeds over 2.5 mm long; perianth 4.5 mm or more long; largest capsules 5–7 mm long.

J. stygius

9. Inflorescence with more than 4 flowers; seeds less than 1.5 mm long; perianth less than 4.5 mm long; capsules under 5 mm long.

10. Ends of seeds with white “tails” about half as long as the slender body; sepals ca. (3.5–) 4 mm long; longest involucral bract 1–6 (–9.5) cm long, often less than 3 cm.

J. vaseyi

10. Ends of seeds without “tails” or these at most half the width of the plump body; sepals (2.2–) 3–3.5 (–4) mm long; longest involucral bract to 21 cm long, usually more than 3 cm.

J. greenei

7. Leaf blades flat, or mostly involute (but then clearly channeled to the end).

11. Flowers in close heads of 2 or more; leaves obviously flat almost their entire length, 1.5 mm or more wide.

12. Leaves with their edge towards the stem (equitant, as in Iris).

J. ensifolius

12. Leaves with their flat side towards the stems.

13. Inflorescence with fewer than 30 heads; stamens shorter than sepals, shriveling in maturity.

J. marginatus

13. Inflorescence with more than 30 heads; stamens about as long as the sepals (or longer), the anthers conspicuous and ± exserted in fruit.

J. biflorus

11. Flowers not in heads, mostly individually pediceled or sessile on branches of the inflorescence (flowers crowded in some rare forms, but at least a few of them clearly single); leaves often involute for much or all of their length, usually less than 1.5 mm wide.

14. Blades of some foliage or involucral leaves arising near the middle of the plant.

15. Inflorescence 1/3–2/3 the height of the plant; sepals acuminate, spreading, distinctly exceeding the capsules, green (or brownish in age) to the tips, with hyaline margins; plant a tufted annual with fibrous roots.

16. Inner tepals acute to acuminate, the tepal midvein not excurrent as a short mucro, usually longer than the capsule; common native.

J. bufonius

16. Inner tepals rounded to acute, but with the tepal midvein often excurrent as a short mucro, mostly shorter than to ± equaling the capsule; rare alien.

J. ranarius

15. Inflorescence much less than 1/3 the height of the plant; sepals obtuse and incurved with deep brown areas at the tip, scarcely longer (often shorter) than the mature capsule; plant perennial from a rhizome.

17. Anthers ± equaling to ca. twice as long as the filaments; mature capsules conspicuously exceeding the perianth; longest involucral bract often greatly exceeding inflorescence.

J. compressus

17. Anthers 2–4 times as long as the filaments; mature capsules ± equaling the perianth, longest involucral bract usually shorter than or ± equaling the inflorescence.

J. gerardii

14. Blades of foliage leaves all basal or nearly so, arising from lower 1/5 of plant; involucral leaves limited to upper 1/3 of plant.

18. Auricles only slightly prolonged, the free portion rounded, at most up to 0.6 mm long, at least the lower portion thickened, yellow or brownish and often shiny.

19. Auricles thickened, yellow or brownish, and shiny all the way to their margins; stems smooth.

J. dudleyi

19. Auricles grading to a thin ± whitish translucent margin, thickened and yellow only near the base; stems clearly ridged.

J. dichotomus

18. Auricles at summit of leaf sheath (at least the upper ones) conspicuously prolonged, with free portion (0.5–) 1–3 (–5) mm long, very thin, membranous, and fragile, pale whitish or with a smoky patch.

20. Unbranched terminal sections of inflorescence relatively compact, 1–3 (–4)-flowered, the longest distance between adjacent flowers (excluding peduncle) 0.5–5.5 mm.

J. tenuis

20. Unbranched terminal sections of inflorescence (at least the longest) laxly 2–5-flowered, the longest distance between adjacent flowers (excluding peduncle) 6–11 mm.

J. anthelatus

6. Leaf blades ± terete [may be flattened in pressing], hollow with hard cross-partitions at regular intervals [easily felt by running one’s fingernail along a leaf laid on a hard smooth surface, if not evident in dry leaf].

21. Flowers single (or some on a plant in 2’s or rarely in 3’s), some or all often reduced to bulblets; inflorescence usually 1/4 or more the height of the plant, which is generally under 20 cm (very rarely as tall as 30 cm).

J. pelocarpus (in part)

21. Flowers in heads of 2 or more; inflorescences usually less than 1/4 the height of the plant, which is often over 30 (nearly always over 20) cm tall (unusually small or depauperate individuals as small as 10 cm).

22. Seeds with a long or short pale appendage or “tail,” formed by prolongation of the seed coat, at both ends.

23. Majority of heads on a plant consisting of 5–many flowers each, often densely hemispherical or nearly spherical; perianth segments tapering to very sharp points; mature capsules often equaling or only slightly exceeding the perianth (although sometimes much longer); plants stout, over (usually much over) 30 cm tall.

J. canadensis

23. Majority of heads on a plant consisting of 2–5 (–7) flowers each, narrower than hemispherical; perianth segments (tepals) sharp-pointed or blunt; mature capsules much exceeding the perianth; plants slender, usually (15–) 20 cm or more tall.

24. Perianth (1.5–) 2–2.5 mm long; tepals ± blunt or rounded at the tip, with hyaline margins often half the width of the central portion; branches of the inflorescence often divaricate or spreading.

J. brachycephalus

24. Perianth 2.5–3.5 mm long; tepals (at least the sepals) sharp-pointed, with narrower hyaline margins (usually less than 1/2 the width of the central portion); branches of the inflorescence erect or ascending.

J. brevicaudatus

22. Seeds without pale “tails,” either blunt or with small dark points at one or both ends.

25. Stamens 3, opposite the sepals.

26. Mature capsule slender, tapering gradually to a prominent beak 0.5–1 mm long, exceeding tips of sepals; heads densely spherical or almost so.

27. Mature well developed heads 712 mm in diameter; tepals ca. 2–3 mm long; capsules ca. 3–4 mm long.

J. scirpoides

27. Mature well developed heads 1215 mm in diameter; tepals 3.5– 4.5 mm long; capsules 4.5–5.5 mm long.

J. validus

26. Mature capsule plump, shorter than the sepals (rarely much longer), ± abruptly terminating in a very short tip; heads spherical or (in more common species) narrower.

28. Capsules much shorter than sepals; heads densely spherical.

J. brachycarpus

28. Capsules about equaling sepals; heads usually hemispherical or narrower.

J. acuminatus

25. Stamens 6, opposite the petals and sepals.

29. Heads ± spherical, the lower flowers reflexed; involucral bract exceeding the inflorescence; capsule slender, (3–) 3.5 times or more as long as wide, thickest at base, tapering rather regularly to apex.

30. Sepals 4–5.5 (–6) mm long, usually slightly exceeding the petals; largest heads often over 1 cm in diameter; auricles at summit of sheaths of cauline leaves over 1.5 mm long.

J. torreyi

30. Sepals 2.5–3.5 mm long, usually slightly shorter than the petals; heads under 1 cm in diameter; auricles shorter than 1.5 mm (very rarely longer).

J. nodosus

29. Heads hemispherical or narrower, the lower flowers not reflexed; involucral bract shorter than inflorescence (though cauline leaf may exceed it); capsules plump, less than 3 times as long as wide.

31. Plants stout, over 50 cm tall; cauline leaf 1, overtopping the inflorescence, a bladeless (or at most a very short-bladed) sheath on stem between inflorescence and sheath of the cauline leaf.

J. militaris

31. Plants more slender, very rarely as tall as 50 cm; cauline sheaths all with blades, these not overtopping the inflorescence.

32. Petals 1.5–2.5 mm long, ± blunt or rounded at apex, slightly but noticeably shorter than sepals; branches of inflorescence ascending.

J. alpinoarticulatus

32. Petals 2–3 mm long, sharp-pointed at apex, about the length of the sepals or often slightly longer; at least some branches of inflorescence usually spreading.

J. articulatus