Herbs, annual or perennial, often diminutive. Stems erect or procumbent, usually striate, usually unbranched, sometimes branched, 10–40(–150) cm, uncinate-puberulent and sparsely pubescent or glabres­cent. Leaves trifoliolate, usually unifoliolate proximally and/or distally; stipules persistent, patent or deflexed, subulate to narrowly ovate-deltate, 1–7 mm; petiole 10–35 mm; leaflet blades polymorphic between proximal and/or distal ones and median ones in a single individual, linear, narrowly to broadly ovate, rhombic or transversely ovate, lateral leaflets nearly as large as terminal, apex acute to acuminate or obtuse, surfaces uncinate-puberulent and villous; terminal blade 25–50 × 6–10 mm, length 0.8–10 times width; unifoliolate blades transversely elliptic or depressed ovate, 10 × 15–20 mm, or ovate or oblong to broadly ovate, 2–4 × 2–3 mm. Inflorescences branched or unbranched; rachis densely patent uncinate-puberulent; primary bracts caducous or persistent, narrowly ovate, 1.5–5.5 mm. Pedicels 6–23 mm. Flowers: calyx 2–3 mm, scabrous, often glandular, tube 1 mm; abaxial lobes 1.5–2 mm, lateral lobes 1.3–1.5 mm; corolla ephemeral, pinkish or rose-violet, fading yellow-green or blue-green, 2.5–3.5 mm. Loments: margins involute, sutures subequally crenate, contorted or appearing spirally twisted when young; connections central, 1/4–1/5 as broad as segments; segments (1 or)2–5, rhombic, 2–4 × 2–3 mm, angled abaxially, sometimes rounded, obtusely angled adaxially, uncinate-puberulent throughout; stipe 0.3–3.5 mm.

Distribution

United States, Mexico, West Indies, Central America, n South America, introduced in Asia, Africa.

Discussion

Varieties 5 (2 in the flora).

Desmodium procumbens was characterized by B. G. Schubert (1940, 1980) and R. McVaugh (1987) as an erect or procumbent annual species. It was grouped by D. Isely (1998) with D. neomexicanum A. Gray and D. rosei B. G. Schubert in the D. procumbens Group. Desmodium neomexicanum is united with D. procumbens in having twisted loments and is here recognized at the rank of variety.

Selected References

None.

Lower Taxa

Desmodium procumbens var. neomexicanum, Desmodium procumbens var. procumbens

Key

1	Loments distinctly spirally twisted when young, stipes 1.5–3.5 mm; primary bracts 1.5–2.5 mm; leaves unifoliolate and trifoliolate.	Desmodium procumbens var. procumbens
1	Loments slightly spirally twisted, stipes 0.3–2 mm; primary bracts 2.5–5.5 mm; leaves mostly trifoliolate.	Desmodium procumbens var. neomexicanum