4. Echinacea purpurea (L.) Moench (purple coneflower)

Pl. 277 e, f; Map 1174

Plants with a short rootstock and fibrous roots. Stems 50–150 cm long, unbranched or with few to several ascending branches, sparsely to moderately pubescent with stiff, appressed or ascending, broad-based (often pustular-based) hairs. Leaves with the margins usually irregularly toothed and pubescent with ascending hairs, the surfaces moderately to densely pubescent with stiff, appressed to loosely appressed, usually minutely pustular-based hairs, slightly to more commonly moderately roughened to the touch, with (3)5 main veins. Basal leaves 8–45 cm long, the blade narrowly ovate to broadly ovate, mostly 1.5–5.0 times as long as wide, often rounded or cordate at the base. Stem leaves 4–35 cm long, mostly narrowly ovate to broadly ovate, short-tapered to more or less rounded at the base, otherwise similar to the basal leaves. Involucral bracts 7–12 mm long, the outer surface glabrous (except along the margins) or sparsely to moderately pubescent with loosely appressed hairs, not glandular. Receptacle 2–4 cm in diameter, the chaffy bracts 9–15 mm long, somewhat hardened and leathery, usually orange or reddish-tinged toward the tip. Ray florets with the corolla 3–8 cm long, 7–14(–19) mm wide, spreading to somewhat drooping at flowering, pink to purple (rarely white). Disc florets with the corolla 4.5–6.0 mm long, the tube green, the lobes green or purplish-tinged. Pollen yellow when fresh. Fruits 3–5 mm long. 2n=22. May–October.

Scattered nearly throughout the state but uncommon or absent from the Mississippi Lowlands Division and the western portion of the Glaciated Plains (eastern U.S. west to Kansas and Texas; introduced sporadically farther west and north). Mesic to dry upland forests, savannas, upland prairies, ledges and tops of bluffs, banks of streams, and rarely fens and sinkholes; also pastures, old fields, railroads, and roadsides.

The name E. purpurea as used here was officially conserved at the 2005 International Botanical Congress. Binns et al. (2001a, b) had pointed out that when Linnaeus originally described Rudbeckia purpurea L. he was referring to plants from the eastern United States that most modern botanists have called E. laevigata (C.L. Boynton & Beadle) S.F. Blake.

This species is commonly cultivated as an ornamental in gardens, and a number of hybrids and cultivars are available commercially. Rare plants with white ray corollas occur as isolated individuals within some populations and have been called f. liggettii Steyerm. Occasionally, plants are observed in gardens and in the wild with abnormal heads of two main types. Plants exposed to excess water through flooding or overwatering early in the growing season sometimes develop crested heads in which the disc becomes irregularly enlarged, broadened, and somewhat flattened. It is not known whether this condition is caused by direct injury to the meristems of the developing flowering stems or whether waterlogging leaves the plants susceptible to infection by some fungus or other microorganism. Another problem that occasionally afflicts E. purpurea plants (and also a variety of other unrelated crop and wild plants) is known as aster yellows and is caused by a group of prokaryotic microorganisms called aster yellows phytoplasmas (Candidatus Phytoplasma), which reside in the phloem of infected plants and are spread between plants by foraging leafhoppers of the genus Macrosteles Fieber (Delahaut, 1997; Lee et al., 2004; IRPCM Phytoplasma/Spiroplasma Working TeamPhytoplasma Taxonomy Group, 2004). Diseased plants generally have stunted or twisted, often chlorotic foliage, and the corollas often are malformed and greenish. Frequently the disc in infected plants has irregularly elongate stalks with small, headlike clusters of sterile disc florets at the tips. As there is no cure for this condition, plants in a garden should be removed to minimize the risk of spreading the infection.