Herbs, annual [perennial], unarmed, [sometimes base woody]. Stems erect to procumbent or decumbent, glabrous or glabrate to pubescent. Leaves alternate, odd-pinnate; stipules present; petiolate; leaflets 3, blade margins dentate or denticulate, [entire, toothed at base, dissected, or laciniate], surfaces glabrous or sparsely pubescent. Inflorescences pedunculate or subsessile, 1–30-flowered, axillary, racemes or flowers subsolitary, [heads or umbels]; bracts absent. Flowers papilionaceous; calyx campanulate, symmetric or with 2 larger lobes, lobes 5; corolla yellow to white, sometimes tinged violet, or pale to lilac-blue, 5.5–18 mm; stamens 10, diadelphous; anthers dorsifixed; style usually relatively long. Fruits legumes, yellow to light brown, stipitate, sometimes compressed, linear and subterete, ovoid, or rhomboid-obovoid [reniform, lunate, semicircular, moniliform], not coiled, often curved [or prickly], [margins rarely winged or fimbriate], usually beaked, dehiscent, sometimes tardily so, thickly leathery, glabrous or sparsely pubescent. Seeds 1–20[–40], oblong or ovoid, usually tuberculate or verrucose, sometimes smooth. x = 8.

Distribution

Introduced; Eurasia, n Africa, Australia.

Discussion

Species ca. 50 (4 in the flora).

Several Trigonella species are known in the flora area only from ballast collections or as waifs. Trigonella monspeliaca Linnaeus and T. polycarpa Boissier & Heldreich were reported as waifs on chrome ore piles in Maryland by C. F. Reed (1964). Reports of T. laciniata Linnaeus, T. noeana Boissier, and T. hamosa Linnaeus (as “T. ramosa”) by C. H. Knowlton and W. Deane (1918) in Massachusetts could not be substantiated.

Trigonella has been an umbrella genus. More than two dozen species were transferred recently to Medicago. Molecular analyses (G. Bena et al. 1998; M. F. Wojciechowski et al. 2000; K. P. Steele and Wojciechowski 2003; Wojciechowski 2003) have suggested that at least some of the species of Trigonella and Melilotus belong to the same clade, and, accordingly, the two genera need to be combined. More extensive analysis is desirable to support their amalgamation.

Selected References

None.

Lower Taxa

Trigonella caerulea, Trigonella corniculata, Trigonella foenum-graecum, Trigonella procumbens

Key

1	Inflorescences 1- or 2-flowered (in axils), subsessile; peduncles not evident.	Trigonella foenum-graecum
1	Inflorescences 10–30-flowered; peduncles 1.5–6 cm.	> 2
2	Legumes (including beaks) 10+ mm; seeds 4–8; corollas yellow.	Trigonella corniculata
2	Legumes (including beaks) less than 10 mm; seeds 1–3; corollas blue, pale blue, lilac-blue, or white.	> 3
3	Inflorescences globose racemes, slightly elongated in fruit; leaflet blades ovate to oblong.	Trigonella caerulea
3	Inflorescences globose or subglobose to ovoid racemes, elongated in fruit; leaflet blades oblong to linear-oblong or linear-lanceolate.	Trigonella procumbens