Northern Prairie Wildlife Research Center
Central and western North Dakota is home to pulse milk-vetch. The plant has not been recorded in the Red River Valley or our southeastern and northeastern counties. Elsewhere, the plant occurs from northeastern Manitoba to Yukon, south to Michigan, Nebraska, Colorado, and Nevada at elevations up to 11,000 ft.
Pulse milk-vetch is perennial from a branched base atop a woody taproot. North Dakota specimens usually occur as diffuse bushy clumps of thin stems about 1-2 feet tall. Leaves are 2-3 inches long and pinnate, like two combs held back-to-back, because of 11-21 narrow leaflets up to an inch long. The 1/2 inch-long flowers are like those of the pea, only white or yellowish, with purplish keels and banner petals. Flowers are found in loose clusters (racemes) of 5-15 that occur mostly near the top of the plant. Mature fruits (legumes) about 1/2 inch long hold the brown, purple-spotted seeds.
Look for pulse milk-vetch in July on rocky or gravelly native prairie. The plant is not listed among the milk-vetches that can poison livestock, and may have some forage value, as more plants seem to occur where grazing is light or moderate. Many milk-vetches are used in candies, gums, cosmetics, medicines, teas, and for treatment of fabrics, but pulse milk-vetch is not mentioned in this regard.
Pulse 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 tenellus means "delicate" in botanical Latin. Pulse milk-vetch was first described for science in 1814 by Frederick Pursh, who was the first to publish on the many new plants collected by the Lewis and Clark Expedition of 1804-1806.