URBANA, Ill. – With all the “buzz” about bees and butterflies, the Perennial Plant Association is celebrating a plant known for its ability to support birds and insects, including a beloved North American native butterfly. The Association has just announced Asclepias tuberosa as its 2017 Perennial Plant of the Year™.
Commonly known as butterfly weed, this long-lived and striking perennial is native to much of the continental United States, along with Canadian provinces Ontario and Quebec.
“With vibrant orange, red, and yellow flowers that seem to jump out at you, butterfly weed is a great addition to a sunny garden with average to dry soils,” says University of Illinois Extension educator Martha Smith. “As the common name suggests, these plants are butterfly magnets. They also have a medicinal history as a treatment for pleurisy, a common ailment in early colonial times, causing wheezing, coughing, and great pain due to the inflammation of the pleura round the lungs. Asclepias tuberosa reportedly was so effective in treating this ailment it earned the common name pleurisy root.”
Butterfly weed is a member of the Apocynaceae or milkweed family. This family includes plants with a milky sap poisonous to most insects. Unlike other milkweeds, Asclepias tuberosa contains little sap. The hairy leaves are 2 to 5 inches long, growing close together as they spiral up the hairy stem. Stems are branched near the top with flat clusters, or umbels, of many showy flowers in late spring through mid-July.
“Butterfly weed flowers are easy to recognize because of their ‘five up and five down’ appearance,” Smith says. “Each flower has five colorful petals that hang down and five upright curved petals called hoods, each possessing one orange horn. When cross-pollinated, a dry fruit, called a follicle, forms. The mature follicle opens along one side to disperse the seeds.”
Smith recommends deadheading Asclepias tuberosa to prevent reseeding, to keep the plants more attractive, and to promote a second flush of color later in the season.
Asclepias tuberosa makes excellent, long-lasting cut flowers. “Cut stems when more than half the flowers are open; buds do not open well once the stem is cut. Searing the cut end is not necessary to prevent sap from seeping out of the stems. Instead, cut flowers have a good vase life if they are immediately placed in warm water after cutting and either placing stems in a refrigerator for 12 hours or transferring the stems to cold water. This process eliminates what little sap may be produced,” Smith notes.
Butterfly weed is hardy to zones 4-9 and reaches 2 to 3 feet high with a 2-foot spread. Smith cautions gardeners to be patient, as butterfly weed is slow to emerge in the spring. Young plants grow from a single central stem, but with age, plants will develop additional shoots at the base. Mature plants do not transplant well, although they can be divided carefully in early spring before new growth begins. “Dig carefully,” Smith says, “but if enough root is left behind, they will regrow. Don’t cut back in late fall, rather wait until early spring. To prepare young butterfly weed for the winter, put mulch down around them to prevent frost heaving.”
Butterfly weed is often grown from seed. Experts report 50-80 percent germination if fresh cleaned seed is used. “If germination does not occur after 3 to 4 weeks, provide a 2 to 4 week cooling period,” Smith says. “Collected seed will result in flower color variation. To ensure color, purchase seed from a reputable source. Propagation through root cuttings can be used to ensure quality from forms showing merit. Cutting back once, early in the growth cycle, will promote compact growth.”
Since Asclepias tuberosa is a native prairie plant, butterfly weed is quite comfortable in meadow gardens, native plantings, and wildlife sanctuaries, but it is finding its way into semi-formal to formal urban gardens. Smith suggests planting it in large masses, for an unrivaled display of eye-popping orange flower color. Orange butterfly weed pairs well with summer blooming Phlox, Hemerocallis sp., Liatris spicata, Echinacea sp., Salvia sp., and most June/July sun-loving perennials. Another bonus is that if the garden is visited by deer, they will leave Asclepias tuberosa alone.
Many bees, wasps, ants, butterflies, and beetles visit butterfly weed, as well as hummingbirds. All members of the milkweed family serve as larval food for the monarch butterfly (Danaus plexippus), queen butterfly (Danaus gilppus), and the milkweed tussock moth (Euchaetes egle). “Let them munch on butterfly weed and you will be rewarded with these ‘flowers of the air,’” Smith says.