Montana Field Guide

PLANTS: A short, perennial forb from a branched caudex. The nearly leafless stems (acaulescent) are prostrate, 5–10 cm, clothed in stipules. Herbage is wooly-villous which gives the plant a silvery-grey appearance

LEAVES: Pinnately compound leaves are about 12 cm long, weakly ascending or erect. The 9-13 leaflets are oval-orbicular, oblanceolate to lanceolate with rounded to acute tips. Stipules are lanceolate, 3–10 mm long, and separate from each other.

INFLORESCENCE: A short, tightly congested raceme that appears somewhat umbellate-like and terminates a leafless peduncle, usually less than 10 cm long. The inflorescence of 3-10 flowers is erect, about as tall as the leaves, but often lays on the ground in fruit. Flowers are 18-25 mm long. Petals are either
dull white except for the purple tinged keel tip (seldom is the banner and wing tips lavender) or magenta. The banner petal is 18–25 mm long and moderately reflexed. The keel petal is 15–20 mm long. Sepals are 2–5 mm long with black and/or white villous hairs>

Montana’s plants are of variety purshii or concinnus.

Sources: Lesica et. al 2012; Giblin et al. [eds.] 2018.

In Montana Astragalus purshii has two varieties (Lesica et al. 2012):

* var. purshii has creamy-white to pale lavendar flowers (petals) that are 18-25 mm long. The legumes are nearly straight. It is found in grasslands and sagebrush steppe in the plains and valley zones of Montana.

* var. concinnus has magenta flowers (petals) that are 18-20 mm long. Legumes are curved. It is mostly found in the sagebrush steppe of the montane zone within southwest Montana.

Var. purshii is found in grasslands and sagebrush steppe in the plains and valley zones of Montana.

POLLINATORS
The following animal species have been reported as pollinators of this plant species or its genus where their geographic ranges overlap: Bombus vagans, Bombus appositus, Bombus auricomus, Bombus bifarius, Bombus borealis, Bombus centralis, Bombus fervidus, Bombus flavifrons, Bombus huntii, Bombus mixtus, Bombus nevadensis, Bombus rufocinctus, Bombus ternarius, Bombus terricola, Bombus occidentalis, Bombus pensylvanicus, Bombus griseocollis, and Bombus insularis (Macior 1974, Thorp et al. 1983, Mayer et al. 2000, Colla and Dumesh 2010, Wilson et al. 2010, Koch et al. 2012, Miller-Struttmann and Galen 2014, Williams et al. 2014).

FRUIT [Source: Lesica et al. 2012]
The ovary has dense, long, and soft hairs. The legume is 12-25 mm long, retains the dense long hairs, and is tipped with a sharp beak. The legume is also narrowly ovoid (compressed perpendicular to the septum) in shape.