General: multistemmed perennial, 30-60 cm tall, with thick woody roots, from almost hairless (except among the flowers), our variety, to grayish-woolly-hairy throughout, glandular-dotted with small pits.
Leaves: alternate, odd-pinnate, the 3-7 leaflets linear, mostly 10-20 mm long and 1-2 mm broad, folded up length-wise. Stipules small, linear, bristle-like.
Flowers: numerous in narrow, dense spikes 2-7 cm tall and about 1.5 cm thick, the bracts long-pointed, slightly exceeding the buds. Calyx densely woolly- to stiff-hairy and grayish to rusty, the tube 2.5-3 mm long, concealed by the hairiness, the 5 teeth narrowly triangular, shorter than the tube. Corolla purple, sometimes very pale, irregular, apparently of 5 petals, one (probably the only true petal) larger and joined at base to the calyx, the other 4 (due to their position almost surely staminodia) joined to the short staminal tube and alternate with the 5 fertile stamens.
Fruits: pods, 1- or 2-seeded, not splitting, usually contained in the calyx.
Dry plains and foothills, in n.w., c. and e. parts of MT. Also on the e. slope of the Rocky Mts. to Sask. and Manitoba, s. to CO, TX and AL.
The root of purple prairie-clover was used for chewing by several native tribes. It is said to have a pleasant, sweet flavor. The dried leaves have been used as a tea substitute.
The Montana Indians used a poultice of the steeped bruised leaves to be applied to fresh wounds. The Chippewa Indians made a decoction of the leaves and blossoms to be used in the treatment of heart problems. The Meskwaki Indians used it to treat diarrhea, and they also made an infusion of the roots in the treatment of measles. The Navajo used the plant to treat pneumonia.
The tough, elastic stems have been made into brooms.
Our specimen belong to var. purpurea Vent., a greenish, sparsely hairy to almost hairless form.