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.
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.
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.
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.
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.
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.
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.
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.
8. Terminal leaflet with longer petiolule than the lateral leaflets (at least a short extension of the rachis, and of similar color and texture, in addition to the pulvinus); leaflets stipellate or not.
15. Stems ± vine-like, twining or trailing.
16. Leaflets less than 2.5 cm long, without stipels; fruit 1-seeded.
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.
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.
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.
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.
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.
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.
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).
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.
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.
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.
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.
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.
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.
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.
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.
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.
34. Leaves twice pinnately compound; flowers pink or greenish-white, regular, in spherical axillary heads.
35. Flowers greenish-white; plant unarmed; fruits glabrous.
35. Flowers pink; plant armed with stiff ± recurved prickles; fruits bristly.
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.
38. Leaflets of best-developed leaves 9–35 (–40) mm broad, in 3–8 pairs; stamens ca. 7.
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.
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.
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.
45. Inflorescence a simple spike or raceme.
48. Stem vine-like, twining; principal leaflets ca. 1.5–4 cm wide, acuminate; inflorescences all axillary.
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.
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.
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.
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.