Fabaceae

This is one of the largest and most important families of flowering plants in the world, including major food and forage crops as well as some ornamentals and timber trees. Because of the difficulty in interpreting technical characters involving stamens and other parts when flowers are pressed and dry, the keys stress vegetative characters. See Isely (1998) for a synthesis of this family in North America. Glycyrrhiza lepidota Pursh, wild licorice, is known as an adventive in southern Ontario, as well as being native in Ontario northwest of Lake Superior, and could well be found in Michigan. It is a large plant, resembling our Astragalus species, or Galega, but differing in its gland-dotted foliage and spiny fruit.

1. Leaves all simple or apparently so (or absent at flowering time).

2. Plant woody, the vegetative parts glabrous; petals pink, conspicuously exceeding the sepals; flowers in small sessile umbelliform racemes borne on old wood and opening in May (mostly before the leaves); leaf blades ovate to rotund, ± cordate; fruit flat, ca. 5–9 cm long.

Cercis

2. Plant herbaceous, the vegetative parts hairy; petals yellow, shorter than the sepals; flowers few, in small peduncled racemes, opening in mid- or late summer (after the leaves); leaf blades narrowly elliptic to lanceolate, tapering to both ends; fruit inflated, ca. 1.3–2.5 (–4) cm long.

Crotalaria

1. Leaves all or mostly compound (upper leaves simple in Cytisus with distinctive, green, ridged woody stems).

3. Leaflets 3 (except for the rare “4-leaved clover”).

4. Margins of leaflets minutely to strongly toothed, at least at the apex (or with unusually prominent vein tips giving the appearance of toothing).

5. Inflorescences ca. (2–) 4–15 times as long as wide; stipules setaceous, entire, 1-veined, glabrous or nearly so, the free portion over 8 times as long as wide.

Melilotus

5. Inflorescences ca. 2 (rarely 3) times as long as wide, or shorter; stipules with distinct flat blades at least 2–3-veined, sometimes hairy and sometimes toothed, usually less than 8 times as long as wide (a long setaceous very hairy tip in Trifolium arvense).

6. Leaflets all sessile or with petiolules (the pulvini) of uniform length.

Trifolium (in part)

6. Leaflets with terminal one on distinctly longer petiolule than the others.

7. Calyx with glabrous tube and the teeth very unequal (the longest often ca. twice as long as the shortest); stipules entire; fruit ovate-oblong, straight, enclosed in the persistent corolla.

Trifolium (in part, couplet 9)

7. Calyx with hairy tube and the teeth often ± equal; stipules usually somewhat toothed, at least toward base; fruit reniform or elongate, ± curved, the corolla deciduous.

Medicago

4. Margins of leaflets entire.

8. Terminal leaflet with petiolule (if any) no longer than those of the lateral leaflets; leaflets not stipellate.

9. Leaflets dotted with dark glands, linear, ca. 0.5–1.7 mm broad.

Dalea (in part)

9. Leaflets not dotted, more than 1.7 mm broad.

10. Flowers in long-peduncled umbellate inflorescences; leaves glabrous or nearly so (actually 5-foliolate but appearing 3-foliolate with the lowest pair of the sessile leaf suggesting stipules about as large as the other leaflets).

Lotus (in part)

10. Flowers in racemes, small axillary clusters, dense clusters, or solitary; leaves pubescent or glabrous (3-foliolate with small stipules except in one pubescent species).

11. Leaves of upper branches all or mostly simple; stems woody, strongly ridged or angled; flowers yellow.

Cytisus

11. Leaves all trifoliolate; stems herbaceous, lacking prominent ridges; flowers various.

12. Flowers in dense ovoid to ± spherical heads.

Trifolium (in part)

12. Flowers in open, peduncled racemes or solitary or few in leaf axils.

13. Flowers in an open, peduncled raceme terminating the stem (and often branches); fruit many-seeded, inflated; stamens distinct.

Baptisia

13. Flowers solitary or few in leaf axils; fruit 1-seeded, flattened; stamens diadelphous.

14. Stipules conspicuous, ovate, brownish, strongly striate, persistent, much exceeding the petioles; calyx lobes rounded; lateral veins of leaflets strongly parallel, running to the margins; annuals.

Kummerowia

14. Stipules inconspicuous, narrowly triangular to subulate, at most 3-veined, deciduous, the length various; calyx lobes elongate, sharp-pointed; lateral veins of leaflets ± branched and anastomosing before reaching the margins; perennials.

Lespedeza cuneata

8. Terminal leaflet with petiolule longer than those of the lateral leaflets; leaflets stipellate or not.

15. Stems ± vine-like, twining or trailing.

16. Leaflets less than 2.5 cm long, without stipels; fruit 1-seeded.

Lespedeza procumbens

16. Leaflets mostly more than (2.5–) 3 cm long, stipellate; fruit with more than 1 seed.

17. Leaflets suborbicular, at least as broad as long, very broadly rounded at apex; fruit of 1-seeded indehiscent segments covered with tiny hooked hairs.

Desmodium rotundifolium

17. Leaflets longer than broad, usually acute to acuminate; fruit neither segmented nor covered with hooked hairs, usually longitudinally dehiscent.

18. Stems and petioles glabrous.

Vigna

18. Stems and petioles at least sparsely pubescent.

19. Midvein of leaflets not excurrent; flowers without bractlets beneath (not to be confused with bracts at base of pedicel); plants with cleistogamous apetalous flowers at base (often setting 1-seeded fruit underground); calyx ± equally 4-toothed.

Amphicarpaea

19. Midvein of each leaflet excurrent as a minute non-green bristle; flowers subtended by a pair of bractlets; plants without cleistogamous flowers or underground fruit; calyx 5-lobed or ± 2-lipped.

20. Stipels ca. 4–11 mm long; keel of corolla nearly straight; fruit bristly pubescent with long spreading hairs at maturity.

Pueraria

20. Stipels ca. 1–3 mm long; keel of corolla strongly arched, twisted, or coiled; fruit glabrous or sparsely short or appressed pubescent at maturity.

21. Keel of corolla twisted or coiled at the tip; calyx lobes all shorter than the tube; seeds glabrous; leaflets not lobed.

Phaseolus (in part)

21. Keel of corolla strongly arched but not twisted; calyx lobes (at least the longest) longer than the tube; seeds densely woolly; leaflets often broadly 2–3-lobed.

Strophostyles

15. Stems erect, ± straight.

22. Calyx lobes ± deltoid or rounded, much shorter than the tube; stipels none (or vestigial); fruit long-stalked above the calyx.

Hylodesmum

22. Calyx lobes triangular to lanceolate, equaling or longer than the tube; stipels present or not; fruit sessile or stalked only slightly above the calyx.

23. Leaflets without stipels; calyx not bilabiate, all 5 lobes definite (the lower sometimes longer); fruit 1-seeded, glabrous or variously pubescent.

24. Flowers in terminal spike-like racemes, on peduncles longer than subtending leaves; leaflets lance-elliptic, mostly 3 or more times as long as broad, gland-dotted (as are calyx and bracts).

Orbexilum

24. Flowers few or crowded in dense inflorescences, axillary as well as terminal, on peduncles often shorter than subtending leaves; leaflets various, but broadly rounded or oblong-elliptic in species with long-peduncled inflorescences and not gland-dotted.

Lespedeza (in part)

23. Leaflets stipellate; calyx appearing somewhat 2-lipped, the upper 2 calyx teeth ± united, the lower 3 more deeply divided and longer; fruit 2–several-seeded, with spreading pubescence.

25. Fruit composed of (1–) 2 or more 1-seeded, flat, indehiscent segments covered with tiny hooked hairs; stem and axis of inflorescence (unless glabrous) also with minute hooked hairs; native perennial.

Desmodium

25. Fruit not segmented, ultimately dehiscent, covered with straight (or curly) hairs; stem and axis of inflorescence without hooked hairs or these long (many times as long as thick); cultivated annuals, rarely spread from fields.

26. Stems, petioles, and fruit glabrate or with some scattered long (sometimes hooked) hairs.

Phaseolus (in part)

26. Stems, petioles, and fruit densely pubescent with long sharp-tipped hairs.

Glycine

3. Leaflets (i.e., flat blades, not necessarily including tendrils) 2, or 4 or more.

27. Plant a tree, shrub, or woody vine.

28. Leaves even-pinnate (if leaflets not opposite, appearing falsely odd-pinnate), sometimes twice-pinnate.

29. Flowers yellow, papilionaceous; fruit straight, slender, ca. 3–5.5 cm long, dehiscent into twisted valves; leaves strictly once-pinnate.

Caragana

29. Flowers greenish white, regular or nearly so; fruit often somewhat curved, ca. 2–4 cm wide, (6–) 10–35 (–45) cm long, tardily if at all dehiscent; leaves often (especially on vigorous shoots) twice-pinnate.

30. Leaflets entire, ovate with rounded sides and short-acuminate tip, mostly 2–4 cm broad when mature; fruit ca. 3–4.5 cm broad, (6–) 10–15 cm long; flowers all bisexual.

Gymnocladus

30. Leaflets obscurely crenulate with dark glands, lance-oblong, less than 1.5 cm broad; fruit ca. 2–3 cm broad, 18–35 (–45) cm long; flowers both bisexual and unisexual.

Gleditsia

28. Leaves clearly odd-pinnate (and leaflets nearly or quite in opposite pairs, except for the odd terminal one).

31. Plant a high-climbing vine; leaflets often as broad as 3–4 cm, short-acuminate.

Wisteria

31. Plant a shrub or tree; leaflets less than 3 cm broad, rounded at apex.

32. Flowers less than 1 cm long, in narrow, elongate, erect, spike-like racemes; petal 1, blue to purple; fruit less than 1 cm long, indehiscent, 1–2-seeded; low shrubs or if tall, with leaflets gland-dotted beneath.

Amorpha

32. Flowers ca. 1.5–2.8 cm long, in broad ± pendent or spreading racemes; petals 5 in typical papilionaceous flower, white or pink to rose-red; fruit ca. (3.5–) 4.5–10 cm long, 3–several-seeded; tall shrubs or trees, the leaflets not gland-dotted.

Robinia

27. Plant an herb (at most somewhat woody at the ground).

33. Leaves palmately or twice-pinnately compound.

34. Leaves palmately compound; flowers blue (rarely rose or white), papilionaceous, in terminal racemes.

Lupinus

34. Leaves twice pinnately compound; flowers pink or greenish-white, regular, in spherical axillary heads.

35. Flowers greenish-white; plant unarmed; fruits glabrous.

Desmanthus

35. Flowers pink; plant armed with stiff ± recurved prickles; fruits bristly.

Mimosa

33. Leaves once-pinnately compound.

36. Leaves with an even number of leaflets, the terminal one at most represented by a bristle or tendril.

37. Terminal “leaflet” a bristle or none; flowers yellow, slightly irregular but not papilionaceous; stamens 5–10, separate; petioles with a prominent gland near the base (or on the rachis at the lowest pair of leaflets).

38. Leaflets of best-developed leaves 1–5 mm broad, in 10–21 or more pairs; stamens 5 or 10.

Chamaecrista

38. Leaflets of best-developed leaves 9–35 (–40) mm broad, in 3–8 pairs; stamens ca. 7.

Senna

37. Terminal leaflet replaced by a well-developed tendril; flowers various in color but not yellow in most species and clearly papilionaceous; stamens united (diadelphous, 9+1 or 5+5); petioles without glands.

39. Stipules larger (both longer and broader) than the lowest leaflets.

Pisum

39. Stipules smaller than lowest leaflets (narrower or shorter, usually both).

40. Leaflets 2 (not including tendrils).

Lathyrus (in part, couplet 5)

40. Leaflets 4 or more.

41. Larger stipules at least (7–) 10 mm broad (hastate or semi-sagittate); principal leaflets at least 1.2 cm broad.

Lathyrus (in part)

41. Larger stipules less than 7 mm broad (semi-sagittate or lanceolate); principal leaflets in most species all less than 1 cm broad.

42. Leaflets with 10 or more pairs of lateral veins running from the midrib nearly or quite to the margins (some somewhat faint in the rare weed V. lathyroides).

Vicia (in part)

42. Leaflets with 6 or fewer pairs of lateral veins.

43. Leaflets mostly 10 or more, less than 8 (–9) mm broad, less than 3 cm long; stem wingless.

Vicia (in part)

43. Leaflets mostly 4–8, or at least 8 mm broad (or both), over 2.5 cm long; stem in some forms narrowly winged.

Lathyrus (in part, couplet 4)

36. Leaves odd-pinnate, the terminal leaflet developed.

44. Leaflets linear to oblanceolate-elliptic, mostly less than 3 mm wide, covered with prominent glandular dots; inflorescence a dense cylindrical spike of tiny (less than 9 mm long) flowers.

Dalea (in part)

44. Leaflets broader (mostly at least 4 mm wide), glandless; inflorescence various, of larger flowers.

45. Inflorescence an umbel or involucrate head.

46. Stem and calyx pubescent; flowers in a head subtended by 3–4-cleft bracts; terminal leaflet often distinctly larger than the lateral ones.

Anthyllis

46. Stem and calyx glabrous or nearly so; flowers in an umbel, essentially bractless or subtended by a trifoliolate leaf; terminal leaflet about equaling the lateral ones.

47. Flowers yellow (to orange); leaflets 5 (the lower pair resembling stipules); fruit dehiscent.

Lotus (in part)

47. Flowers pink (to purple); leaflets numerous; fruit breaking transversely into 1-seeded indehiscent segments.

Securigera

45. Inflorescence a simple spike or raceme.

48. Stem vine-like, twining; principal leaflets ca. 1.5–4 cm wide, acuminate; inflorescences all axillary.

Apios

48. Stem erect or ascending, not twining; principal leaflets less than 1 (–1.5) cm wide, obtuse, rounded or notched at apex (except for excurrent mid-vein); inflorescences terminal or axillary.

49. Racemes all or mostly terminal; flowers 14–20 mm long, bicolored with yellow standard and pink to purple wings; stem, rachis of leaves, calyx, and fruit densely villous with simple mostly spreading hairs; calyx lobes longer than the tube.

Tephrosia

49. Racemes all or mostly axillary; flowers 10–14 (–15) mm long, uniformly white or cream to purplish; stem, rachis of leaves, calyx, and fruit glabrous or nearly so or strigose with straight or forked hairs.

50. Leaflets with the midvein prolonged as a conspicuous bristle ca. 1–2.5 mm long; calyx glabrous or at most a few hairs on the bristle-like lobes.

Galega

50. Leaflets lacking bristle tips, at most with a short apiculus less than 0.5 mm long; calyx variously pubescent.

51. Fruit not segmented, 4.5–15 mm broad; flowers white to cream.

Astragalus

51. Fruit segmented (as in Desmodium, but glabrous) with 2 or more distinct and very narrow constrictions, less than 6 mm broad; flowers pink or magenta.

Hedysarum

All species found in Fabaceae

Amorpha canescensLEAD-PLANT 
Amorpha fruticosaFALSE INDIGO 
Amphicarpaea bracteataHOG-PEANUT 
Anthyllis vulnerariaWOUNDWORT 
Apios americanaINDIAN-POTATO, GROUNDNUT, WILD-BEAN 
Astragalus canadensisCANADIAN MILK-VETCH 
Astragalus cicerCHICK-PEA MILK-VETCH 
Astragalus neglectusCOOPER'S MILK-VETCH 
Baptisia lacteaWHITE FALSE INDIGO 
Baptisia leucophaeaCREAM WILD INDIGO 
Baptisia tinctoriaWILD INDIGO 
Caragana arborescensPEA-TREE 
Cercis canadensisREDBUD, JUDAS TREE 
Chamaecrista fasciculataPARTRIDGE-PEA 
Chamaecrista nictitansWILD SENSITIVE-PLANT 
Crotalaria sagittalisRATTLEBOX 
Cytisus scopariusSCOTCH BROOM 
Dalea leporinaPRAIRIE-CLOVER 
Dalea purpureaPURPLE PRAIRIE-CLOVER 
Desmanthus illinoensisILLINOIS BUNDLEFLOWER 
Desmodium canadenseSHOWY TICK-TREFOIL 
Desmodium canescensHOARY TICK-TREFOIL 
Desmodium ciliareHAIRY TICK-TREFOIL 
Desmodium cuspidatumSMOOTH-BRACTED TICK-TREFOIL 
Desmodium glabellumTICK-TREFOIL 
Desmodium illinoensePRAIRIE TICK-TREFOIL 
Desmodium marilandicumSMALL-LEAVED TICK-TREFOIL 
Desmodium obtusumSTIFF TICK-TREFOIL 
Desmodium paniculatumPANICLED TICK-TREFOIL 
Desmodium perplexumTICK-TREFOIL 
Desmodium rotundifoliumROUND-LEAVED TICK-TREFOIL 
Desmodium sessilifoliumSESSILE-LEAVED TICK-TREFOIL 
Galega officinalisGOATS-RUE, PROFESSOR-WEED 
Gleditsia triacanthosHONEY LOCUST 
Glycine maxSOYBEAN 
Gymnocladus dioicusKENTUCKY COFFEE-TREE 
Hedysarum alpinumALPINE SAINFOIN 
Hylodesmum glutinosumCLUSTERED-LEAVED TICK-TREFOIL 
Hylodesmum nudiflorumNAKED TICK-TREFOIL 
Kummerowia stipulaceaKOREAN BUSH-CLOVER 
Lathyrus hirsutusWILD PEA 
Lathyrus japonicusBEACH PEA 
Lathyrus latifoliusPERENNIAL PEA, EVERLASTING PEA 
Lathyrus ochroleucusPALE VETCHLING 
Lathyrus odoratusSWEET PEA 
Lathyrus palustrisMARSH PEA 
Lathyrus pratensisYELLOW VETCHLING 
Lathyrus sylvestrisPERENNIAL PEA, EVERLASTING PEA 
Lathyrus tuberosusTUBEROUS VETCHLING 
Lathyrus venosusVEINY PEA 
Lespedeza bicolorSHRUBBY LESPEDEZA 
Lespedeza capitataROUND-HEADED BUSH-CLOVER 
Lespedeza cuneataSERICEA, SERICEA LESPEDEZA 
Lespedeza frutescensVIOLET BUSH-CLOVER 
Lespedeza hirtaHAIRY BUSH-CLOVER 
Lespedeza procumbensTRAILING BUSH-CLOVER 
Lespedeza thunbergiiJAPANESE BUSH-CLOVER 
Lespedeza violaceaBUSH-CLOVER 
Lespedeza virginicaSLENDER BUSH-CLOVER 
Lotus corniculatusBIRDFOOT TREFOIL 
Lupinus perennisWILD LUPINE 
Lupinus polycarpusLUPINE 
Lupinus polyphyllusGARDEN LUPINE 
Medicago lupulinaBLACK MEDICK 
Medicago polymorphaBUR-CLOVER 
Medicago sativaALFALFA 
Melilotus albusWHITE SWEET-CLOVER 
Melilotus altissimusTALL SWEET-CLOVER 
Melilotus officinalisYELLOW SWEET-CLOVER 
Mimosa quadrivalvisSENSITIVE BRIER, CAT-CLAW 
Orbexilum pedunculatumSAMPSON'S SNAKEROOT 
Phaseolus polystachiosWILD BEAN 
Phaseolus vulgarisGREEN BEAN, STRING BEAN, SNAP BEAN, KIDNEY BEAN, WAX BEAN, COMMON BEAN 
Pisum sativumCOMMON PEA, GARDEN PEA, GREEN PEA, FIELD PEA 
Pueraria montanaKUDZU 
Robinia hispidaBRISTLY LOCUST, ROSE-ACACIA 
Robinia pseudoacaciaBLACK LOCUST 
Robinia viscosaCLAMMY LOCUST 
Securigera variaCROWN-VETCH 
Senna hebecarpaWILD SENNA 
Senna toraSICKLE-POD 
Strophostyles helvulaWILD BEAN 
Tephrosia virginianaGOATS-RUE, RABBIT-PEA 
Trifolium arvenseRABBITFOOT CLOVER 
Trifolium aureumHOP CLOVER 
Trifolium campestreLOW HOP CLOVER 
Trifolium depauperatumCLOVER 
Trifolium dubiumLITTLE HOP CLOVER 
Trifolium fucatumCLOVER 
Trifolium hybridumALSIKE CLOVER 
Trifolium incarnatumCRIMSON CLOVER 
Trifolium pratenseRED CLOVER 
Trifolium repensWHITE CLOVER 
Vicia americanaAMERICAN VETCH 
Vicia carolinianaPALE VETCH, WOOD VETCH 
Vicia craccaBIRD VETCH 
Vicia grandifloraLARGE-FLOWERED VETCH 
Vicia hirsutaHAIRY VETCH 
Vicia lathyroidesSPRING VETCH 
Vicia sativaCOMMON VETCH 
Vicia sepiumHEDGE VETCH 
Vicia tetraspermaSPARROW VETCH 
Vicia villosaHAIRY VETCH 
Vigna unguiculataCOW PEA; BLACK-EYED PEA 
Wisteria frutescensWISTERIA 
Wisteria sinensisCHINESE WISTERIA 

Citation:

MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. October 19, 2017. http://michiganflora.net/family.aspx?id=Fabaceae.