Drummond's Milkvetch
Astragalus drummondii Dougl. ex Hook.
Family: Fabaceae, Pea
Genus: Astragalus
Synonyms:
Other names:
Nomenclature: drummondii = named after Drummond
Nativity / Invasiveness: Montana native plant
Poisonous plant
No medicinal data
Description

General: grayish-long-stiff-hairy perennial from a heavy root and branched crown, usually with several erect, branched stems 40-70 cm tall.

Leaves: alternate, 6-14 cm long, the 13-31 leaflets ovate to oblong or linear-elliptic, 2-3.5 cm long, 2-10 mm broad, long-hairy on the lower surface, hairless above. Stipules almost membranous, 3-12 mm long, the lowest either fully clasping stem and joined into a sheath around 2/3 of the stem, the upper ones lance-pointed, always free.

Flowers: about 20 to 50 in considerably elongate clusters, the main stalks about as long as the leaves. The individual flower stalks 1-3 mm long. Flowers pale whitish, sometimes with a purplish-tipped keel, 18-25 mm long. Calyx finely black-hairy, 8-11 mm long, the teeth about half as long as the tube. Banner not much bent back from the narrow wings which are 4-6 mm longer than the keel. June-July.

Fruits: pods, hairless, drooping, with a stalk-like support about equal to the calyx, the body 2-4 cm long, 4-5 mm broad, broadly cordate in section, the lower seam deeply intruded to form a nearly complete partition.


Distribution

Dry hillsides, plains and foothills, in most parts of MT. Also in the plains region on the e. side of the Rockies from Saskatchewan and Alberta to ID, UT and NM.
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.


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