Davis Milkweed is a distinctive native plant with unique botanical characteristics, playing an important role within its ecosystems. It contributes to the biodiversity of its native range. This profile explores its features, natural environment, and ecological contributions.
Identifying Davis Milkweed
Davis Milkweed (Asclepias cryptoceras ssp. davisii) is an herbaceous perennial known for its low growth habit. Stems typically measure between 10 to 30 centimeters, often trailing along the ground. Its leaves are arranged oppositely on the stem, measuring 2 to 6 centimeters long and nearly as wide. These leaves are obovate to oval in shape, sometimes ovate-lanceolate, and often feature conspicuous hairs along their margins.
The plant produces umbellate inflorescences, which are umbrella-like clusters of flowers, usually located at the stem’s tip. Each central cluster contains 5 to 10 individual flowers. The flowers themselves are pale greenish-yellow, with some lobes often tinged with red on their back. Pinkish hoods, 5 to 6 millimeters long, enclose the anthers. It generally blooms from April through June.
Natural Habitat and Distribution
Davis Milkweed thrives in dry hills and lower mountain areas. It prefers specific soil types, including basalt scree, gravelly clay, or silt. These environments are typically open and feature steep, bare slopes. Elevations where it is found range from approximately 400 to 730 meters (1310 to 2395 feet) in certain regions.
This milkweed subspecies is naturally distributed across a specific geographical area in the western United States. Its range extends from southeastern Washington, south through eastern Oregon and eastern California, and into central Nevada and southern Idaho. Historically, it has also been reported in northwestern Wyoming. In Washington, it is primarily known from the Blue Mountains ecoregion within Asotin County.
Ecological Importance
Davis Milkweed serves as a host plant for monarch butterfly larvae. Monarch caterpillars feed exclusively on milkweed leaves, relying on these plants for their development. The plant’s milky sap contains cardiac glycosides, which the caterpillars absorb, making them unpalatable to many predators. Without milkweed, monarch butterflies cannot successfully reproduce or complete their transformation.
Beyond its role as a host plant, Davis Milkweed flowers provide a nectar source for a wide array of pollinators. These include various native bees, honey bees, and other butterfly species. Moths, skippers, beetles, and flies also visit the flowers to collect nectar. The presence of milkweeds in an ecosystem also attracts beneficial insects, such as mite-eating ladybeetles, minute pirate bugs, hover flies, and parasitic wasps.
Conservation Status and Efforts
While specific conservation designations for Davis Milkweed may vary by state or region, many native milkweed populations face challenges. Habitat loss is a significant threat, often resulting from agricultural expansion and urban development. Invasive grasses can outcompete native milkweeds, further reducing available habitat.
Degradation of existing habitats also occurs due to activities like right-of-way construction and maintenance for roads and utilities. These factors collectively contribute to the fragmentation and reduction of suitable environments for milkweed species. Conservation efforts focus on protecting remaining native habitats and restoring degraded areas. Supporting native plant initiatives and planting milkweed species appropriate to local ecosystems are practical ways individuals can contribute.