Species: Common milkweed
Scientific name: Asclepias syriaca
Claim to fame: As the interest in butterfly gardening continues to increase, so does the popularity of common milkweed. This plant’s symbiotic relationship to the monarch butterfly has made this native wildflower a favorite of people who like to see this orange-and-black insect flutter in their yards each summer. The milky latex found in the plant’s stems was also long-purported to help rid a human’s skin of warts, moles and a number of skin conditions; but this is disputed in the medical world. A number of Native American tribes crushed the plant’s dried stalks and used the resulting fibers to make strong ropes.
Species status: Common milkweed is abundant throughout most of Missouri.
First discovered: One of the earliest descriptions of common milkweed comes from Canadensium planetarium historia, a description of Canadian plants written by French physician Jacques Philippe Cornut in 1635. The famed naturalist Carl Linnaeus used this pioneering plant book as a source for writing his taxonomic description of the plant in the 18th century.
Family matters: Common milkweed belongs to the plant family Asclepiadaceae. A common trait shared by many of the approximately 2,000 species of herbs and shrubs in this group is that they have milky sap.
Height: up to five feet
Flowers: Common milkweed has small pinkish-white flowers arranged in large rounded clusters at the tops of the stems and just below the tops of the stems. Each flower is about a quarter-inch in diameter with five reflexed petals (“reflexed” means the petals curve or bend backwards). These petals surround five hood-like appendages, each hood having a tiny pointed “horn” rising from it.
Seeds/fruits: The plant’s fruits are pods that are up to four inches long. Each pod is filled with small dark brown seeds, each seed being attached to a tuft of silky hair.
Distinguishing characteristics: Besides the large flower clusters and, later in summer, the pods bearing the “hairy” seeds; another identifying characteristic of a milkweed plant is the thick, leathery leaves that are long (up to 8 inches) and are arranged opposite of each other on the stem. The stem is unbranched and has fine hairs. Tearing away the leaves will cause milky sap to ooze from the opening – hence the name “milkweed.” Common milkweed, as well as most of North America’s other species of milkweed plants, have a unique relationship with the monarch butterfly. This connection begins when monarch caterpillars feed on the leaves of milkweed plants. The ingestion of the plant’s toxic juices makes the caterpillars and the ensuing butterflies unpalatable to birds. As a result, monarchs are able to complete their pollination and migration duties without fear of predation from birds, which instinctually avoid them.
Annual/biennial/perennial: Common milkweed is a perennial.
Habitat: Included among the preferred habitats for common milkweed plants are pastures, old fields, degraded prairies and roadsides.
Life cycle: After flowering, the plant produces seed pods which dry and open. Wind is the primary agent of dispersal of the seeds.