Asclepiadaceae : Asclepias tuberosa
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Family Name
Asclepiadaceae
Common Name
Butterfly milkweed
Description
Asclepias tuberosa is a perennial herb with milky white sap, growing from a deep rootstock with 1 to many stems arising from thick crown. The stems are simple to having a few branches toward the top, generally covered with short hairs, and reaching 30 to 90 cm in height. The ascending to spreading simple leaves are alternate on the lower stem but become subopposite to opposite where the flowers emerge. The blades are entire, linear to broadly lanceolate, 5-10 cm long and 7-23 mm wide with margins that curl downward. There are 1 to several umbellate clusters of flowers at the ends of the stem and branches and in the upper leaf axils. Six to 25 flowers are attached to a short peduncle (< 3 cm long) or sessile with each flower having a short (12-19mm) pedicel. Flowers are 11-16 mm long, the calyx is covered with hairs and green to purplish colored, with lobes 2-4 mm long. The bright orange to reddish corolla lobes are reflexed and 5.5-8.5 mm long. The fused stamens and pistil is about 1-1.5 mm tall and wide. The fruit are tapered at both ends, 8-15 cm long and 1-1.5 cm wide. The seeds are oval 5-7 mm long with long white hairs. Butterfly milkweed blooms from May to August in sandy prairies and open woodlands in a few counties in both eastern and western South Dakota.
Horticulture Notes
Seed Collection: Collect seeds when the pods turn brownish and begin to open in the late summer or early fall.
Germination: Seeds require a moist cold treatment before germinating. Planting out in the fall or 30 days in moist soil in the refrigerator will allow them to grow.
Vegetative Propagation: Established plants can be subdivided in the spring.
Light: Full sun.
Soil: Prefers well-drained sandy soils. Although drought tolerant the plants do best with moderate watering.
Additional Notes
Butterfly milkweed makes a beautiful cut flower and is an attractive addition to a native plant garden. The bright orange blooms attract butterflies and hummingbirds and the foliage plays host to monarch and other butterfly larvae.