Plains Milkvetch
Astragalus gilviflorus Sheldon
Family: Fabaceae, Pea
Genus: Astragalus
Other names: three-leaved milkvetch
Nomenclature: gilviflorus = pale yellow flowered
Nativity / Invasiveness: Montana native plant
Poisonous plant
No medicinal data

General: tufted, cushioned, almost stemless perennial from a branched, woody root crown, silvery-flat-stiff-hairy with T-shaped hairs. Stems 1-3 cm long, densely cushioned with old stipules and stalks.

Leaves: basal, 2-6 cm long, rarely up to 10 cm, long-stalked, the 3 leaflets elliptic to oblanceolate or obovate, 8-20, rarely 35 mm long. Stipules membranous, pointed, 6-15 mm long.

Flowers: mostly 1 or 2, almost stalkless in the leaf axils, about 20-30 mm long. Calyx silvery-flat-silky-hairy, 2/3-3/4 the length of the corolla, the awl-shaped teeth about 1/3 as long as the tube. The corolla ochroleucous to yellow, sometimes purplish-tipped, the keel purple-tipped, much shorter than the wings. June-July.

Fruits: pods, stalkless, leathery, ovoid, 7-10 mm long, scarcely equaling the calyx, flat-silky-hairy, not opening, rounded to oval in section.


Dry, gravelly sites on the plains, in most parts of MT except the extreme w. parts. Also along the e. base of the Rocky Mts., from Sask. and NE to CO.
Poisonous Properties

A large, diverse number of milkvetches endemic to North America are considered toxic to both livestock and wildlife, often producing behaviors in poisoned animals described as "crazy", hence the common name "locoweed" ("loco" is Spanish for "crazy") often given to many species. The poisonous species have been historically divided into three groups: those species that produce nitrotoxins, those that accumulate the element selenium, and those that produce alkaloids known as "locoine" or "swainsonine". Nitrotoxins, such as 3-nitro propanol, are produced by a large number of species in the western North America, but only a relatively few species have high enough concentrations to actually poison livestock grazing on them. The toxic nitro-containing compounds as well as their glycoside derivatives disrupt normal functions of the central nervous system, often leading to paralysis and death. Some 25 North American species of Astragalus have been identified as selenium accumulators. These species concentrate the element selenium (Se) in their tissues to toxic levels. The third type of poisoning and probably the most severe, called "locoweed poisoning" or "locoism", is caused by several species of Astragalus and a few species of Oxytropis which synthesize the alkaloid swainsonine. When eaten, swainsonine inhibits cellular enzymes (mannosidases) and produces an intoxicating, addictive response, ultimately leading to weight loss and impaired locomotor functions, resulting in ataxia and death.

Sub taxa:

Our specimen belong to var. robustior Hook.

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