Commonly known as butterfly weed, this long-lived and striking perennial is native to the continental United States (except for the northeast) along with the Canadian provinces Ontario and Quebec. With vibrant orange/red/yellow flowers that seem to jump out, butterfly weed is a great addition to a sunny garden with average to dry soils. As the common name suggests, these plants are butterfly magnets.
They also have a medicinal history as 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 another common name, pleurisy root.
Butterfly weed is a member of 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 leaves are 2-5” long, more or less alternate, growing closely together spiraling up the stem, hairy, unserrated, lanceolate, sessile or lacking leaf petiole and appearing attached to the stem. Leaves are dark green on top, lighter green beneath. Stems are hairy and branched near the top with at clusters (umbels) of many showy flowers in late spring through mid-July.
Butterfly weed flowers are easy to recognize because of their “5 up & 5 down” appearance. Each flower has 5 colorful petals that hang down, and 5 upright curved petals called hoods, each possessing one horn. Horns are more or less orange, erect, sickle shaped, inward curved, forming within the hood. When cross-pollinated a dry fruit forms. This dried fruit, also called a follicle, opens along one side to disperse the seeds. It is 4-5” long and only 1⁄2”-3/4” wide, with a smooth surface. Initially green, they mature brown and split open to release the seeds. Deadheading Asclepias tuberosa is recommended to prevent reseeding, keeping the plants more attractive and promoting a second push 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.
Mature plants do not transplant well so proper siting is important. Young plants develop from a single central stem but with age plants will tiller (develop shoots) at the base, sending up multiple erect stems from a large taproot extending down a foot or more. Due to the taproot, division is difficult but can be done in early spring before new growth begins. Butterfly weed is hardy to zones 4-9 and reaches 2-3’ high with about a 2’ spread. Don’t cut back in late fall; rather wait until early spring. Mulching young plants prevents frost heaving. Be patient since butterfly weed is slow to emerge in the spring.
Butterfly weed is often grown from seed. Experts report 50-80% germination if fresh cleaned seed is used. If germination does not occur after 3-4 weeks provide a 2-4 week cooling period. 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 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 is finding its way into more formal to semi-formal urban gardens. Plant in large masses, for an unrivaled display of eye-popping orange flower color. Butterfly weed pairs well with summer blooming Phlox, Hemerocallis, Liatris, Echinacea, Salvia, and most of June/July sun loving perennials. Another bonus is that deer will leave Asclepias tuberosa alone!