Asclepiadaceae : Asclepias pumila

Asclepias pumila is a perennial herb with milky white sap, which grows from a taproot or slender rhizome with 1 to several stems arising from a branched base and reaching 8 cm to 30 cm in height. The leaves are simple, alternate in a tight spiral and often whorled near the base of the stem. The blade is narrow 1.5-6 cm long and about 1 mm wide, erect to spreading, lacks a petiole and the margin is entire. There are 1 to many inflorescences in the axils of the upper leaves, each with 4-20 flowers in an umbellate cyme. The flowers are 5-8 mm long, the calyx green to purple with 5 lobes. The corolla is white to pink tinged or sometimes a yellow green, reflexed and 2.8-4.2 mm long. The fruit are follicles that are erect, narrow cylinders 4-6 cm long and 6-8 mm wide. The seeds are ovate 4-6 mm long with long white hairs that turn brown with age. As with other milkweeds the stamens and pistils are fused, greenish-white and 0.6 to1.1 mm tall. Plains milkweed blooms from July to September in prairies and along hillsides throughout South Dakota.