Inflorescences axillary, pedunculate, umbellate to racemose, few- to many-flowered; bracts small, persistent; bracteoles absent. Flowers with an explosive tripping mechanism. Calyx campanulate, with 5 equal to subequal teeth. Standard obovate, longest; wings and keel obtuse. Stamens diadelphous; filaments not dilated; anthers uniform.
Pod 1- to many-seeded, scarcely dehiscent, tightly coiled or rarely reniform or falcate, often with a row of spines or tubercules on the dorsal suture which is formed of a thickened region of central and lateral veins; seeds without a conspicuous aril.
Most species were introduced as pasture plants and have become naturalized on disturbed sites such as roadsides, gardens, lawns and in pastures.
| | Key to the species | |
| 1 | Pods neither spiny nor tuberculate | 2 |
| Pods tuberculate to spiny | 7 |
| 2 | Inflorescences 10–50-flowered; peduncles more than twice as long as subtending petioles | 3 |
| Inflorescences 1–10-flowered (rarely to 15-flowered in Medicago tornata); peduncles less than twice as long as subtending petioles
Back to 1 | 4 |
| 3 | Pods reniform, with only the distal end coiled, 1-seeded; corolla yellow; standard 2–2.5 mm long | Medicago lupulina |
| Pods cylindrical, 2–3-coiled, 2–6-seeded; corolla violet; standard 6–12.5 mm long
Back to 2 | Medicago sativa |
| 4 | Pods 11–17 mm diam., lateral veins not visible | 5 |
| Pods 2.5–10 mm diam., lateral veins visible
Back to 2 | 6 |
| 5 | Coils of pods concave, lower coils enclosing upper ones; pods ellipsoid or cup-shaped | Medicago scutellata |
| Coils of pods convex, stacked together on top of one another; pods lenticular
Back to 4 | Medicago orbicularis |
| 6 | Pods with lateral veins separated from dorsal suture by a narrow deep groove; coils with flat sides, 15–20 radial veins per coil | Medicago polymorpha |
| Pods with lateral veins separated from dorsal suture by a flat region; coils with convex sides, c. 10 radial veins per coil
Back to 4 | Medicago tornata |
| 7 | Upper surface of leaflets sparsely to densely hairy when young | 8 |
| Upper surface of leaflets glabrous
Back to 1 | 9 |
| 8 | Stipules hairy only on lower surface, weakly toothed to deeply incised; pods with lateral veins separated from dorsal suture by narrow, deep groove, dorsal suture narrow | Medicago truncatula |
| Stipules hairy on both surfaces, entire to weakly toothed; pods with lateral veins separated from dorsal suture by a broad, slightly concave region, dorsal suture wide
Back to 7 | Medicago minima |
| 9 | At least some leaflets deeply laciniate | Medicago laciniata |
| Leaflets entire to toothed
Back to 7 | 10 |
| 10 | Pods 10–14 mm diam | Medicago intertexta |
| Pods 4–9 mm diam
Back to 9 | 11 |
| 11 | Dorsal suture bisected by a shallow groove; leaflets marked by an upper central blotch or a very wide shield occupying the basal two-thirds of the leaflet | Medicago arabica |
| Dorsal suture not grooved; leaflets either not marked or with darker flecks or a basal darker patch
Back to 10 | 12 |
| 12 | Calyx teeth longer than tube; keel shorter than wings; inflorescences 1–10-flowered; terminal leaflets 8–27 mm long; peduncles shorter than to twice as long as the subtending petioles | Medicago polymorpha |
| Calyx teeth shorter than tube; keel longer than wings; inflorescences 1–3-flowered; terminal leaflets 5.5–12 mm long; peduncles shorter than subtending petioles
Back to 11 | 13 |
| 13 | Standards 4.5–6 mm long; pods 5–6 mm diam., dorsal suture elevated above lateral veins; 7–14-seeded; leaflets oblanceolate | Medicago laciniata |
| Standards 2–3 mm long; pods 4–5 mm diam., dorsal suture level with lateral veins; 3–6-seeded; leaflets obovate to obcordate
Back to 12 | Medicago praecox |
