Astragalus missouriensis (Missouri Milkvetch)
|Also known as:|
|Habitat:||sun; dry prairies, hillsides, bluffs|
|Bloom season:||May - June|
|Plant height:||4 to 6 inches|
|Wetland Indicator Status:||none|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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A short raceme of 3 to 10 stalked, pea-shaped flowers at the end of a hairy 1½ to 4-inch stem. The flowers have a broad, erect upper petal (standard) ½ to nearly 1 inch long, and much smaller lateral petals. Petal color can be almost white but more often rich purple with a large white splash in the center of the upper petal. The calyx is brown, gray or blackish, ¼ to 3/8 inch long with long awl-shaped lobes and covered with short, stiff hairs pressed close to the surface (appressed).
Leaves and stems:
Leaves are compound in groups of 9 to 17, up to 5 inches long, mostly prostrate. Leaflets are oval-elliptic, ¼ to ½ inch long, toothless, blunt or with a small abrupt point at the tip, covered with short, white appressed hairs that give them a silvery to gray-green appearance. The hairs are attached to the surface in the middle of the hair rather than the end, requiring strong magnification to see. The leafy appendages where the compound leaf meets the stem (stipules) are lance-oval, 1/8 to ¼ inch long, attached freely at the base. The multiple stems are prostrate to ascending, the flowering stems mostly prostrate but rising at the tip (decumbent).
The fruit is a short oblong pod ½ to 1 inch long, its surface wrinkled and covered in short stiff hairs.
Minnesota is at the extreme eastern edge of this dry prairie species' range, which runs from Texas and New Mexico up into Canada. Its range within Minnesota is limited to 9 counties on our western end. Never widespread, its requirement of dry gravelly habitat saved it from the plow but pasturing, gravel mining and the encroachment of red cedar, once controlled by prairie fires, continue to threaten its presence in the state. According to the DNR, it was listed as a Special Concern species in 1984. It can be distinguished from other Astragalus species by the gray-green colored leaves from the dense appressed hairs, the large upper petal on the flowers, the low, mostly prostrate growth. There are 4 varieties in North America; var. missourienses is the most common and found in Minnesota.
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Photos by K. Chayka taken in Chippewa County. Photos courtesy Peter M. Dziuk taken in Chippewa and Lac Qui Parle counties.
Have you seen this plant in Minnesota, or have any other comments about it?