Native. Perennial. Propagates by seeds. Time of bloom: June to August. Seed-time: August to October. Range: Ontario to Minnesota, southward to Florida, Texas, and Arizona. Habitat: Dry fields and pastures.
The most showy of the Milkweeds. Where abundant, the plant may be made to pay for the cost of its suppression by the sale of its white, tuberous roots, which are valuable medicinally and bring six to ten cents a pound in the drug market; they should be collected in autumn, when well stored with sustenance for the winter.
Stems several from the clustered tubers, one to two feet high, erect, branched at the top, round, and very hairy; they lack the milky juice so characteristic of the family. Leaves alternate, oblong to lance-shaped, acute or sometimes obtuse at apex, entire, hairy on both sides, sessile or with very short petioles. Flowers in large flat-topped umbels terminating stem and branches, brilliant orange in color; butterflies of many kinds are nearly always hovering about them; the five lower segments of the corolla are reflexed and the crown above it has five small, spreading hoods, each of which has within it a slender, incurving horn. Stamens five, inserted on the base of the corolla, the filaments forming a tube which incloses the pistil, the anthers adherent to the stigma; ovaries two, with very short styles connected at the summit by the disk-like stigma. The fruits are twin follicles, three to five inches long, gray-hairy, pointed at both ends, their pedicels so bent as to hold them nearly erect. Seeds flat, margined, brown, bearing a coma or tuft of long, silky hairs. (Fig. 220.)
Fig. 220.- Butterfly Weed (Asclepias tuberosa). X 1/4.
Persistently deprive the tuberous roots of green growth above ground and they will at length wither and die. Begin cutting before the first flowers mature, and repeat as often as new shoots put forth. Dry salt applied to the shorn surfaces will check new growth.