Desmodium rotundifolium DC.

Desmodium rotundifolium plant

Family - Fabaceae

Stems - Trailing, to +1m long, herbaceous, multiple from the base, branching, scabrous to scabrescent or pilose and short uncinate pubescent.

Leaves - Alternate, petiolate, trifoliolate, stipulate. Stipules large, ovate, acuminate, obliqua at the base, entire, to 1cm long, 7mm broad, mostly glabrous abaxially, pilose on margins and adaxially, green with evident venation. Petioles pubescent as the stem, to +/-4cm long, with swollen basal portion to 4mm long. Lateral leaflets with short petiolules, (2.1mm long). Stiples linear-lanceolate, to 3mm long. Terminal leaflet with petiolule to +/-1.5cm long, stiples same as in the lateral leaflets but slightly smaller. All leaflets basically rotund, the terminal being larger than the laterals, all villous to pilose above and below, to +/-5cm in diameter.

Desmodium rotundifolium leaf

Inflorescence - Axillary loose racemes and panicles in the apical 1/3 of the stems. Stipules somewhat reduced in inflorescence. Axis of inflorescence uncinate pubescent.

Flowers - Corolla papilionaceous. Standard 1cm broad, pinkish purple externally, whitish internally, glabrous, with two small white spots at base surrounded by dark purple. Keels and wings to 9mm long, glabrous. Keels connate. Wings connate basally to keels. Stamens diadelphous, tube glabrous and white. Anthers greenish-yellow, .3-.4mm long. Ovary green, puberulent, 3-4mm long. Style upcurved, 1.5mm long, glabrous, green. Calyx bilabiate. Upper lip single-lobed. Lobed deflexed, acute, triangular, to -2mm long. Lower lip 3-lobed. Lobes triangular-acuminate, -2mm long, mostly equal. Calyx tube -2mm long, pilosulose externally, glabrous internally. Loments typically with 3 segments. Segments to 9mm long, 5mm broad, compressed, densely uncinate pubescent. Stipe 4-5mm long.

Desmodium rotundifolium flower

Flowering - July - September.

Habitat - Acid soils, dry rocky woods, ridges, hilltops.

Origin - Native to U.S.

Other info. - This species can be found in the Southeast half of the state. The plant is easy to ID in the field because of its trailing stems and big rotund leaflets. Another species, D. ochroleucum M. A. Curtis, is similar but exceedingly rare in Missouri. The terminal leaflets of this latter species are not entirely rotund and the plant is more erect than D. rotundifolium.

Photographs taken in Big Spring State Park, 8-20-03.