Oxytropis lambertii (Lambert's Locoweed)
|Also known as:||Purple Locoweed|
|Habitat:||sun; dry prairies and plains|
|Bloom season:||May - June|
|Plant height:||4 to 16 inches|
|Wetland Indicator Status:||GP: UPL MW: FACU NCNE: FACU|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Spike cluster up to 12 inches long on a hairy, leafless stem, with up to 25 flowers in a cluster and typically rising well above the leaves. Flowers are pea-shaped, deep pink to purple later turning blue, about ¾ inch long and stalkless. The erect upper petal (standard) is notched at the tip, sides rolled back, and has a large pale patch in the center streaked with darker lines. The 2 lateral petals fold over a keel that is abruptly tapered to a small projection (“beak”) at the tip. The calyx is 1/3 to ½ inch long, purplish, with short narrow teeth around the tip and covered in long, silky hairs. A small, hairy, leaf-like bract is at the base of the calyx.
Leaves and stems:
Leaves are basal in tight rosettes surrounding or near a flowering stem, mostly erect to ascending, up to about 6 inches long, compound in groups of 9 to 19 leaflets. Leaflets are stalkless, linear-oblong, 1/3 to 1 inch long and covered in long, silky hairs. At the base of each compound leaf stalk is a hairy, lance-linear appendage (stipule), up to about ½ inch long with a sharply pointed tip. Flowering stems are multiple from the base, a plant forming a clump.
Of the 4 Oxytropis species ever recorded in Minnesota, this is the only one likely to be encountered in the wild. Two species—Flat Locoweed (O. campestris) and Showy Locoweed (O. splendens)—are likely extinct in the state and the fourth, Sticky Locoweed (O. viscida, or O. borealis var. viscida) is only known from a single location in Cook County on a north-facing cliff near the Canadian border. O. campestris, a Federally Threatened species, is known from a handful of locations in Wisconsin and is found along sandy lakeshores that have fluctuating water levels. O. spendens, found in the Dakotas westward, has unique compound leaves with whorled leaflets. The locoweeds (Oxytropis species) resemble the related milkvetches (Astragalus species) but are easily distinguished by the beaked keel on the flowers combined with basal leaf clumps surrounded by small stipules, where Astragalus leaves are arranged along the stems and a keel with a rounded or pointed tip but not typically beaked. There are 3 recognized varieties of O. lambertii, 2 of which have limited ranges from Texas to Utah, and var. lambertii found throughout the Great Plains and in Minnesota.
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- Lambert's Locoweed plant
- Lambert's Locoweed habitat
- just coming into bloom
- mature plant
- more leaves
- more flowers
- flowers turning blue
Photos courtesy Peter M. Dziuk taken in Big Stone State Park, Big Stone County, and Glacial Lakes State Park, Pope County.
Have you seen this plant in Minnesota, or have any other comments about it?