Northern Prairie Wildlife Research Center
In North Dakota, only the area southwest of the Missouri River is home to bentflower milk-vetch. This is one of the few plants whose natural distribution is restricted to the northern Great Plains; the species ranges from southern Alberta and Saskatchewan south to South Dakota and Wyoming.
Bent-flowered milk-vetch is a low, bushy branched perennial from a woody taproot. Plants are tufted or matted. Stems are usually only about a foot tall and trailing or only partly erect. The two-inch-long leaves are dissected into 5-17 elliptic leaflets about 1/2-inch long. About 5-11 pale to pinkish-purple flowers are loosely arranged on racemes. Each flower is about 3/8-inch long. At maturity, the legumes (pods) are bent toward the base of the plant. Legumes are about 3/8-inch long and contain smooth, olive-to-black seeds.
This is a rather rare plant, but locally common where found. The species may reach greatest abundance on rocky prairie knolls and ridges. Grazing pressure by cattle seems to have little effect on the abundance of this plant. The species is not listed among the milk-vetches that can poison livestock. Many milk-vetches are used in candies, gums, cosmetics, medicines, teas, and for treatment of fabrics, but bent-flowered milk-vetch is not mentioned in this regard. Bent-flowered milk-vetch is a member of the economically important bean family (Fabaceae). Fab means "bean" in Latin. The generic name Astragalus is an old Greek name of some leguminous plant, and also of the ankle bone. Worldwide, there are about 1,500 species of Astragalus; most are found in the North Temperate and Arctic zones. The specific epithet vexilliflexus means "with the standard (upper central or banner) petal bent" in botanical Latin. Bent-flowered milk-vetch was first described for science by a Minnesotan, Edmund Perry Sheldon (1869-?), expert in the genus Astragalus and author of books on forestry in the Pacific Northwest.