Northern Prairie Wildlife Research Center
A plant of the western half of North Dakota, tine-leaved milk-vetch is a true Great Plains plant whose distribution is limited to the arid grasslands stretching from southern Alberta and southwestern Manitoba to Kansas and Colorado at elevations under 6,500 ft.
Tine-leaved milk-vetch is a coarse perennial with a woody taproot below a subsurface woody caudex. Up to ten stout stems curve upward from the caudex. Stems and leaves have very short hairs throughout. Leaves are few, pale green, and up to four inches long. The leaves are pectinate, or arranged like two combs held back-to-back. Thus each leaf is divided into 4-10 pairs of narrow leaflets up to two inches long. Up to 30 flowers are loosely scattered in racemes at the top of the plant. Flowers are pale yellow and nearly an inch long. At maturity, the plump, inch-long legumes ("pods") are tan and have long, pointed tips. These legumes fill with shiny, pale brown seeds.
Look for tine-leaved milk-vetch during early to mid-June in native grassland, especially on clay or fine gravel soils. Plants are more abundant where grazing pressure is heavy or moderate. This may indicate avoidance, as this poisonous species is one of the more troublesome selenium-accumulators that can cause "blind staggars" in livestock. Fortunately, animals will not consume such plants unless forced to. Many milk-vetches are used for foods, medicines, and gums, but, not surprisingly, I found no mention of such uses for tine-leaved milk-vetch.
This plant 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, 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 pectinatus means "set like a comb" in botanical Latin. Tine-leaved milk-vetch was first described for science in 1830 under another, now obsolete, genus by the eminent British botanist Sir William Jackson Hooker (1785-1865).