O. arvensis: undershrub, low, spreading, much branched, sometimes nearly erect, one foot high or more, with soft spreading hairs, glutinous; leaves trifoliolate, the leaflets obovate or oblong; flowers stalked, solitary, pink, the standard streaked with deeper pink. - Barren pastures. Fl. June to September.
Var. campestris or antiquorum: glabrous, more erect, and usually thorny. - Barren pastures.