It is an annual herb with a stout main root and fibrous lateral roots. The stem is slender, purplish-green, 12-32 cm tall, tetragonal, and sparsely hairy. Leaves vary from pinnate compound below to simple above, with serrate margins.
It is found in Hubei, Sichuan, Shaanxi, Hunan, Guangxi, and Yunnan provinces in China, growing under forests, along roadsides, and on grassy slopes at elevations of 700-2000 meters.
紫色
Var. erythrophylla often has larger leaves mostly basal, usually pinnate compound with 1-2 pairs of leaflets, occasionally simple, with serrate margins. The undersides are purple and both surfaces are sparsely to nearly hairless.