Mourning Milkvetch

Astragalus atratus var. mensanus, commonly known as Mourning Milkvetch, is a perennial herbaceous plant belonging to the legume family, Fabaceae. This variety is native to the western United States, particularly found in regions such as the Great Basin and surrounding areas. It typically grows in dry, rocky soils and is often associated with sagebrush ecosystems. The growth habit of Mourning Milkvetch is characterized by a low, spreading form, reaching heights of approximately 15 to 30 centimeters. The plant forms a dense mat, which can help stabilize soil in its native habitat.

The leaves of Astragalus atratus var. mensanus are pinnately compound, consisting of numerous small leaflets that are lanceolate to ovate in shape, providing a feathery appearance. The flowers are a notable feature, typically appearing in clusters and displaying a range of colors from pale purple to blue. Each flower is characterized by a distinctive banner petal that is larger than the other petals, which aids in attracting pollinators such as bees. The fruit is a legume, which develops into a flattened pod containing several seeds. These pods are often hairy and can be somewhat curved, facilitating seed dispersal.

Ecologically, Mourning Milkvetch plays a significant role in its native habitat by contributing to soil nitrogen levels through its ability to fix atmospheric nitrogen, thanks to symbiotic relationships with rhizobia bacteria. This process enhances soil fertility and supports the growth of other plant species in the area. Additionally, the plant provides forage for various herbivores and serves as a nectar source for pollinators. An interesting adaptation of this species is its drought tolerance, allowing it to survive in arid conditions, which is crucial for its persistence in the often harsh environments of the Great Basin.