Plant of the Week

Map of the United States showing states. States are colored green where the species may be found.
Range map of Astragalus alpinus. States are colored green where the species may be found.

Astragalus alpinus in habit.
Astragalus alpinus in habit, Groundhog Meadow Trail, Colorado. Photo by Al Schneider.

Closeup of the pea-like flowers of Astragalus alpinus.
Closeup of the pea-like flowers of Astragalus alpinus, Groundhog Meadow Trail, Colorado. Photo by Al Schneider.

Fruit pods of Astragalus alpinus.
Drooping, hairy fruit pods of Astragalus alpinus, Groundhog Meadow Trail, Colorado. Photo by Al Schneider.

Alpine Milkvetch (Astragalus alpinus)

By Walter Fertig

According to The Plant Book by D.J. Mabberley, the genus Astragalus in the pea family (Fabaceae) has more species (2000) than any other genus of vascular plant. About 375 species of Astragalus (and many more varieties) occur in North America, with the majority found in the mountains and desert basins of the west. Many Astragali are relatively rare, with small geographic ranges and specialized habitat and soil requirements. Astragalus alpinus is an exception, occurring widely across northern Eurasia, Alaska, and Canada south to Vermont, Minnesota, New Mexico, Nevada, and Oregon.

In Greek, “Astragalos” is the name of the anklebone, and was used by the ancients as dice in games of chance (thus the gambler’s slang term of “bones” for dice). When shaken, the anklebones made a rattling sound, not unlike that of dried fruit pods of many pea species. Linnaeus applied the name to the group of peas commonly called milkvetches or locoweeds. A large number of Astragalus species are poisonous to cattle, sheep, and horses because of their concentration of the element selenium or production of nitrogen-based toxins. Sickened animals may develop deformed hooves or have impaired nervous systems, leading to a condition called blind staggers or locoism. A few Astragalus species have been used medicinally by humans and have recently been touted as promoting longevity by activating the enzyme telomerase, though little clinical evidence supports these claims. Researchers are also studying milkvetch extracts as a potential drug to combat AIDS.

Pea-like flowers with a purple banner and keel and white wing petals characterize Astragalus alpinus (alpine milkvetch). Fruit pods droop at maturity and are covered by short, black and white hairs. Unlike beans and peas, the fruits are dry-textured when mature. Alpine milkvetch is usually found in mountainous meadows, but not typically above timberline as its name would suggest. Botanical historian Roger Williams explains this anomaly by pointing out that the term “alp” originally referred to mountain pastures, and not the rocky and icy peaks commonly associated with the European mountain range of the same name. American botanist Charles Parry was apparently the first botanist to restrict the use of “alpine” to dwarfed species growing in harsh climates at high elevations above tree line. Parry’s usage (published in 1867) has prevailed, to the point where most people have forgotten the original connotation.

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