Description: This is a native perennial plant that is 1½-3' tall. It may develop as a single central stem, particularly when young, or branch outward to form a small bush in appearance. Older plants tiller at the base, with multiple stems emerging from the large taproot. The alternate leaves are medium green or yellowish green, and slightly shiny notwithstanding the presence of tiny hairs. They are linear or broadly linear in shape, about 3" long and ½" wide, with smooth margins. Unlike other milkweeds, this plant has a clear sap, and the level of toxic cardiac glycosides is consistently low (although other toxic compounds may be present).
The erect clusters of bright orange flowers occur at the terminal point of stems toward the top of the plant, and are about 2-4" across. These flowers may bloom intermittently from early to late summer, depending on moisture levels, and are rather long-lasting. There is no floral scent. During late summer, seedpods develop that are about 4-5" long and ¾" thick, with a smooth surface that is slightly hairy. They eventually split open along one side and release the seeds, to which are attached large tufts of white hairs. Dispersion of the seeds is by wind. The root system consists of a woody taproot that is thick and knobby.
Cultivation: The preference is full sun, mesic to dry conditions, and a sandy acid soil. This plant will flourish in other kinds of soil if the site is well-drained, including those that are rocky or contain clay. Sometimes the lower leaves will turn yellow, or the taproot will rot, if there is too much moisture in the ground. Also, if the taproot of a young plant is too close to the soil surface, it may not overwinter successfully due to heaving. Otherwise, Butterfly Milkweed is easy to grow, although somewhat slow to develop.
Range & Habitat: Butterfly Milkweed is fairly common in Illinois, except some areas in western and NW Illinois. Habitats include mesic to dry sand prairies and other kinds of prairies (including black soil), open rocky areas of upland oak forests, sandy Black Oak savannas, shale and sandstone glades (in southern Illinois), abandoned fields, and roadsides.
Faunal Associations: The nectar of the flowers attracts long-tongued bees, Sphecid wasps, and various butterflies, including Swallowtails and Fritillaries. The Ruby-Throated Hummingbird also seeks nectar from the flowers. The caterpillars of Danaus plexippes (Monarch Butterfly) consume the foliage. This plant also attracts other insects, some of which feed exclusively on milkweeds and their relatives. for more information). Mammalian herbivores avoid this and other milkweeds because of the bitterness and toxicity of their leaves.
Comments: This is perhaps the showiest of the milkweeds because of the long-lasting and colorful flowers. It is also the only milkweed in Illinois that produces orange flowers. The thick roots were used for various medicinal purposes in the past.