Field Milk-vetch
Astragalus agrestis
Dougl. ex G. Don
Synonym: A. dasyglottis
Family: Fabaceae, Pea
Genus: Astragalus

low, short-flat-hairy perennial with long rootstocks
from a buried crown. Stems numerous, slender, creeping to
erect, 10-30 cm tall.
Leaves: alternate, 4-10 cm long, the 11-19 leaflets
linear-lanceolate to oblong-lanceolate, often slightly notched
at tips, 1-2 cm long.
Stipules linear to ovate, blunt-tipped,
usually joined around stem at the base.

Flowers: about 7-20 in head-like clusters,
1.5-2.5 cm
broad and as long, from leaf axils. Main flower stalks
to longer than the leaves. Flowers erect, about 17 (13-19)
mm long, the individual stalks thick, scarcely 0.5 mm long.
Calyx about half the length of the corolla, with grayish to
blackish, flat to spreading hairs, the teeth linear, somewhat
shorter than the tube. Corolla usually purplish, or the wings
whitish, the banner narrow, longer than the slender wings
which are about 4 mm longer than the slightly pointed keel.
Flowering time: June-August.
Fruits: pods, stalkless, erect, about 1 cm long, grayish-
to blackish-stiff-hairy, ovoid, heart-shaped in section,
2-celled by the deep groove of the lower seam.

Moist spots in sagebrush plains and montane meadows to
alpine slopes, in most parts of MT. Also from Yukon
southward, on the e. side of the Cascades, from B.C. to n.
CA, NM, e. to Manitoba, MN, IA, and KS, and in e. Asia.

Possibly Toxic plant: see below.
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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.

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