Description
Cup Clover is a hairless annual herb with ascending or erect stems which stand 1-5 dm tall. Small "3-leaf clover" leaves are borne alternately on the stems, each leaf having 2 stipules (appendages) at the base of a long petiole (stalk) which bears 3 leaflets with toothed margins. Clover heads are borne on leafless peduncles (stalks which support an inflorescence) from leaf axils. Each head consists of 5-30 flowers cupped within a shallowly lobed, prominently veined, finely toothed involucre (whorl of bracts, in this case fused together, which subtend an inflorescence); the heads are 5-15 mm long and about the same width. The small flowers are about 2-5 mm long and have bilateral symmetry. The calyx has a 13-20 nerved tube and 5 teeth; the lower 3 teeth each have 2 or 3 bristle-like tips. The white, cream, or pink corolla is about as long as the tips of the calyx teeth, and consists of a banner (the large, hooding, upper segment), the wings (the side segments) and a keel (the prow shaped bottom segment). The fruit is a pod with usually 2 seeds.
Diagnostic Characteristics
Distinguished from other Montana TRIFOLIUM by combining annual habit, flower heads subtended by a shallowly lobed involucre, and lower calyx teeth with 2-3 bristle-tips.