Astragalus bisulcatus
commonly known as the two-grooved milkvetch
Intro and Distribution
Astragalus bisulcatus is a perennial herb native to central and western North America and found in fescue prairies and mixed prairie grasslands of the northern Rocky Mountains and Northern Great Plains. It is abundant in alluvial clay soils, especially those rich in selenium. The two-grooved milkvetch grows between 36-48" tall and is commonly found at elevations of 2,000–7,500 ft.
Characteristics
A. bisulcatus is a member of the Fabaceae family, it is characterized by long pinnate leaves, and pea like purple flowers arranged in elongated racemes. The plant is extremely difficult to identify without its key characteristic for which it was named for: bisulcatus, which in Latin means two-grooved and refers to the shape of the seed pod.
Ecological Information
Because A. bisulcatus most often grows in soils rich in selenium, the plant accumulates large amounts of selenium and results in the production of amino acids containing selenium instead of sulfur. This replacement is actually toxic to cattle and the other animals that eat it. Common symptoms include: ascites, brain vacuolation, a rough and dry coat, cytoplasm vacuolation, depression, dead fetus and kidney vacuolation. Most animals avoid eating A. bisulcatus because of the musky odor produced by the selenium but sheep and cattle often tend to eat the plant and are intoxicated. If the amount ingested is high enough sheep can die within 30 minutes. In Wyoming between 1919 and 1931 A. bisulcatus caused more deaths of cattle and sheep than any other poisonous plant.
