Plains Milk-vetch - Astragalus gilviflorus

Plains Milk-vetch
Astragalus gilviflorus Sheldon

Family: Fabaceae, Pea
Genus: Astragalus

Description
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.
Flowering time: 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.

Distribution
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.

Possibly Toxic plant: see below.

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Contents
Identification
English Names Index
Scientific Names Index
Family Index

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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". Aliphatic nitrotoxins, such as 3-nitro propanol, which 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.

Varieties:

Our specimen belong to var. robustior Hook.