19. Desmodium rubrum (Loureiro) Candolle, Prodr. 2: 327. 1825.
赤山蚂蝗 chi shan ma huang
Ornithopus ruber Loureiro, Fl. Cochinch. 2: 452. 1790; Desmodium carlesii Schindler.
Subshrubs, prostrate or erect, 30-50 cm tall, much branched. Leaves often 1-foliolate, rarely 3-foliolate; petiole 4-10 mm, densely adpressed pubescent; blade elliptic, sometimes narrowly elliptic to nearly orbicular, 1-2.2 cm × 7-12 mm, abaxially sparsely adpressed pubescent, adaxially glabrous, base narrowly cordate, both ends obtuse or apex slightly emarginate. Racemes terminal, 5-25 cm; rachis yellow hooked hairy. Flowers extremely lax. Pedicel 2-3 mm, elongated to 7 mm at fruiting. Calyx often red; lobes nearly equal. Corolla blue or pink, 5-6 mm; standard obcordate, ca. as long as keel; wings obliquely ovate, shorter, auriculate, wholly clawed. Legume narrowly oblong, ca. 2 cm, slightly curved, glabrous, lower suture constricted, upper suture straight, 2-7-jointed; articles nearly quadrate, distinctly reticulate veined. Fl. and fr. Apr-Jun.
Wastelands, sandy areas at seashores; sea level. Guangdong, Guangxi, Hainan [Cambodia, Vietnam].
Because of its long taproot system, this plant is used for protecting riverbanks.