Showy milkweed is a member of the milkweed family Asclepiadaceae (now placed in Apocynaceae, the dogbane family). Showy milkweed is a native herbaceous perennial from widespread rhizomes, which produce stems that grow to 1½ to 5 ft tall in summer. The gray-green leaves are opposite, 4 to 7 inches long, oval, and covered in velvety hairs. Stems and foliage exude milky latex sap when cut. Flowers are in loose clusters at the top of the stems and are rose-purple, aging to yellow. Individual Asclepias flowers look like crowns, with the corolla (petals) reflexed, and hoods above the corolla. Plants flower from May to September. Thick seed pods 3 to 5 inches long split down one side in fall to release reddish-brown, flat seeds. Each seed has a tuft of white, silky hairs that allows them to be dispersed by wind.
Showy milkweed grows in well-drained soil in full or nearly full sun, in pastures, meadows, forest clearings, untilled fields, roadsides, and ditch banks, from sea level to 6,250 ft
Seed can be collected after pods have ripened. Seeds do not store well, and should be sown in the fall, as seedlings are delicate and generally transplant poorly, and potted plants do not overwinter well. Cold, moist stratification for up to three months may improve seed germination in showy milkweed. Showy milkweed has 70,000 to 100,000 seeds per pound, so sowing at a rate of one pound pure live seed per acre will result in 1- 2 seeds per square foot. Propagation by rhizome cuttings is easy and reliable. The cuttings should be dug when the plant is dormant (generally by October). Each piece of rhizome should have at least one bud. Plant the rhizomes 4 to 6 inches deep in late fall. Irrigation the first year will improve survival. Both seedlings and cuttings will usually bloom in the second year, although cuttings will occasionally bloom their first year.
Milkweed stems die in winter, and new stems emerge in spring. For fiber, old milkweed stems were collected by breaking them off at the ground after the leaves dried in fall. Milkweed was burned in the fall by California Indian tribes to eliminate dead stems, stimulate flower and seed production, and stimulate new growth with tall, straight stems and long fibers in the following year.
Pests and Potential Problems
Insects besides butterflies that tolerate milkweed toxins include the large milkweed bug (Oncopeltus fasciatus), common milkweed bug (Lygaeus kalmii), red milkweed beetle (Tetraopes tetrophthalmus), blue milkweed beetle (Chrysochus cobaltinus), and some aphids (Aphis spp.). These insects can occasionally cause feeding damage.
Milkweed plants are toxic to livestock, but animals will avoid them when other forage is available. Milkweed should be excluded from hay or prepared feeds.
Plant description via USDA-NRCS Plant database, Plant Fact Sheet: Showy Milkweed, Asclepias speciosa
Showy Milkweed Extreme Closeup Photo Credit: Bureau of Land Mang Or WA, via Flickr creative commons commercial use
Showy Milkweed Photo Credit: Doug Goldman hosted by the USDA-NRCS PLANTS Database