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Canada Milk-vetch Astragalus canadensis


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Canada Milk-vetch
© Thomas Bentley

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Family: Fabaceae, Pea view all from this family

Description Many whitish to pale yellow or greenish pea flowers, upright or hanging down slightly in dense racemes atop often clustered, leafy stems.
Habit: native perennial herb; smooth, stout stems; rhizomatous and clump-forming.
Height: 12-48 in (0.3-1.2 m) or more.
Leaf: alternate, odd-pinnate, to 12 in (30 cm) long; 13-31 leaflets, 0.5-2 in (1-5 cm) long, broadly lanceolate.
Flower: greenish-white to pale yellow to cream, to 0.75 in (19 mm) long; in upright or nodding spike, to 8 in (20 cm) long, of 24-60 flowerheads.
Fruit: pod, smooth, pointed, woody, held upright, grooved on bottom, to 0.6 in (15 mm) long; two cells; persisting over winter.

Warning All plants in the genus Astragalus are potentially toxic to humans and animals if ingested, causing a disorder called locoism. The milk from an animal that has ingested Astragalus plants may also be toxic. Sensitivity to a toxin varies with a personís age, weight, physical condition, and individual susceptibility. Children are most vulnerable because of their curiosity and small size. Toxicity can vary in a plant according to season, the plantís different parts, and its stage of growth; and plants can absorb toxic substances, such as herbicides, pesticides, and pollutants from the water, air, and soil.

Flower May to September.

Flower May - July (in south); July - August (in north)

Habitat Open, well-drained sites: prairies, open woodlands, forest clearings, stream banks, shore lines, thickets, marshes, roadsides; also grown for restoration and erosion control.

Range Found throughout North America, except for parts of northern Canada, Arizona, Florida, and New England from Nova Scotia south to Rhode Island.

Discussion Three varieties are proposed. Threatened or endangered in Maryland, Michigan, and Vermont. This was the first Astragalus from North America to be scientifically described. Representative of many species with white corollas, several notoriously poisonous, Canada Milk-vetch has toxic compounds but seems not to be a serious pest.

Comments Like other members of the pea family, this plant requires the presense of microorganisms which inhabit nodules on the plant's root system and produce nitrogen compounds necessary for the plant's survival. Soil/seed inoculum is available at most native plant nurseries. This is an aggressive plant and needs competition and/or a watchful eye.

Exposure Preference Partial shade to sun.

Native Distribution S.w. Quebec to Hudson Bay & British Columbia, s. to Georgia mts., Texas, s.w. Utah & n. California

Site Preference Moist to dry prairies; stream banks; open woods

Soil Preference Moist to mesic soils