Asclepias asperula, (Antelope horn, Spider Milkweed)
Mature seed pods curve upward approximating the form of an antelope horn, hence the common name for this species. Leaves are long and fold upward from the central vein in a V. The stem is green tinged with maroon. Erect umbels bear greenish white and maroon flowers that form broad round clusters, strongly contrasting with the bright green leaves.
Distribution: AZ, CA, CO, ID, KS, NE, NM, NV, OK, TX, UT
Flower: Color is greenish-yellow tinged with maroon. Corollas do not reflex backward as in other milkweed species but surround the hoods. Corollas are a light green color, and hoods are white with a maroon tinge at the base. No horns are present. Clusters of flowers are 3-4 in (7 1/2- 10 cm) across. Terminal umbels stand erect. 20+/- flowers per umbel.
Foliage: One to 15 stems arise from a central root crown. Stems erect but those of older plants, in areas without surrounding vegetation, tend to be prostrate, radiating out from the center. Covered with small hairs. Leaf arrangement is whorled or alternate and attachment is sessile or petiolate with a short petiole. Stems produce a single terminal umbel and, if pollination has been successful, several pods can develop per stem.
Habitat: Desert swales, sand and rocky hillsides.
Height: 24-36 in (61-91 ½ cm).
Leaves: Narrow, linear, to lanceolate, 4-8 in (10-20 cm) long. 1-3 in (2 ½-7 ½ cm) wide. Leaf margins fold upward from central vein forming a V.
Blossoming Season: April –August.
Life span: NA
Propagation: By seed.
Pods: Green to purple color, 4-10 in (10-25 ½ cm) long. 2-4 in (5-10 cm)wide.
Seed Color: Brown.
Environment and Growth Requirements
Overhead Conditions: Needs full sun.
Precipitation: Less than 8 in to 50 in (20-127 cm) annually.
Soil Texture: Course, medium, fine. Prefers rocky soils.
Temperature: Can tolerate a minimum temperature of –10 to –20 Fahrenheit (-23 to -29 Celsius).
Work Cited: swbiodiversity.org, Plants.usda.gov, Wildflower.org, Arborday.org, Eduplace.com, Books.google.com (Plants of Arizona by Anne Orth Epple)
Photos: Bobby Gendron