Know Your Natives – Purple Coneflower

Purple Coneflower (Echinacea purpurea) of the Sunflower or Composite (Asteraceae) family is an erect herbaceous perennial with large, showy, terminal flowerheads. The genus name is derived from a Greek word for “hedgehog” in reference to the spiny bracts that share the receptacle with the ray and disk florets. The specific epithet is Latin for “purple,” the color of the ray florets. In the US, the species is common in Arkansas, Missouri and Indiana with more limited occurrence in surrounding states and from Alabama into New England. In Arkansas, plants grow statewide except for the lowlands of the Mississippi Alluvial Plain and West Gulf Coastal Plain. Habitat preference is sunny to partially sunny sites on moist, well drained soils of prairies, open woodlands and borders, and rights-of-way. Other common names include Eastern Purple Coneflower and Broad-Leaved Purple Coneflower.

Photo 1: Showy terminal flowerheads occur singly on main stems and axillary branches. Photo – July 4.

Mature plants develop a central knobby rootstock comprising a clump of shallow “root stubs” supported by fleshy, whitish roots. The root stubs have actively growing crowns with new growth, as well as dormant stems from previous growing seasons. Growth that does not include a stem is flattened and fan-like and produces basal leaves; growth that includes a stem is terete and reproductive, ultimately bearing one or more terminal heads.

Photo 2: This 4-year-old (?) plant has 2 dormant “root stubs” (with dead stems still attached), a stub bearing leaves only (with fan-like base) and 3 stubs (with round bases) bearing leaves and a central stem. Photo – June 25.

The pale-green, stout, erect stems to 3+ feet tall are typically hirsute, uncommonly partially or totally glabrous. Stems taper from a ¼-inch-diameter base, before flaring to the receptacle in support of the flowerhead. Robust plants produce axillary branches at mid-stem that may be 1½ feet long and overtop the main stem. Stems bear single terminal flowerheads, with that of the main stem typically the largest. Stem leaves are generally alternate, but may be sub-opposite to opposite, especially on more robust plants. The upper one-third to one-fifth of stems and branches tends to be leafless. Dead stems, branches and heads persist into the new growth-year.

Leaves vary from small, early, heart-shaped basal leaves to larger basal and stem leaves that are broadly lanceolate below to narrower above. Petioles of basal and lower stem leaves are especially long and may exceed the length of the leaf blade. Leaf bases may be rounded or tapered with the blade extending as narrow wings along the petiole. Larger leaves grow to 14 inches long, including 8-inch petioles, and to 4+ inches wide, typically widest below the middle. Blade margins tend to be entire (smooth) on smaller leaves, but jagged and irregularly serrate on larger leaves. Both upper and lower leaf surfaces may be uniformly covered with dense minute hairs, feeling equally rough, or the upper surface may be markedly less pubescent. Primary veins consist of a straight midrib and a pair of secondary veins that arch from the leaf base to the tip. Veins, including prominent tertiary veins, are recessed above and expressed below.

Photo 3: This year-old plant has broad leaves with short, winged petioles. These leaves are glabrous on their upper surface and pubescent below. Characteristic venation is enhanced by spring-time colors. Photo – March 22.
Photo 4: An older plant, later in the growing season, has ovate to lanceolate leaves with partially winged, longer petioles. Larger leaves have slight marginal serrations. Photo – April 28.
Photo 5: Upper stem leaves become narrower than those below. At this partially shaded site, the plant may not develop branches. Other plants shown include Texas Dutchman’s Pipe, Green Dragon and Nuttall’s Wild Indigo (Baptisia nuttalliana). Photo – May 11.
Photo 6: At a sunny site, mid-stem leaves have jagged, serrated margins. Primary venation consists of the midrib and a pair of arching secondary veins. Caterpillars are those of Pearl Crescents (Phyciodes tharos). Photo – May 23.

The blooming period may extend from late May through July. Early in the growth of flowerheads, buds are spherical with a full cover of hirsute, leafy, lanceolate to linear bracts (often termed phyllaries) imbricated in several series. By flowering time, the phyllaries have become spreading to recurved, resulting in a tight, leafy, saucer-shaped involucre. The longer outermost bracts expand to 1¼ inches long and ⅛ wide.

Flowerheads, 1½ to 4 inches across in bloom, have a central disk of numerous, closely packed disk florets surrounded by 10 to 20 large and prominant ray florets. As in all Composites, bloom sequence is centripetal––from the perimeter toward the center. Disks may be 1½+ inches wide and 1¼+ inches tall, having matured from a flat-topped head at bud-stage to a rounded cone as the final disk florets develop.

Photo 7: Flowerheads initially appear as spherical buds with a full cover of leafy phyllaries. As the central disk expands and becomes more conic, phyllaries are positioned below the flowerhead, forming a saucer-like involucre; this one is 1⅛ inches wide. Photo – June 18.
Photo 8: Final height of branches may exceed the height of the main stem. Solitary flowerheads are terminal. Young flowerheads are rather flat but become conic with age. Photo – June 16.

Ray florets have pink to pale purple, oblong ligules––the showy portion of the ray floret–– that are spreading to recurved and even drooping. Ligules vary from 1¼-3¼ inches long and ¼-¾ inch wide, with a rounded, notched tip. Ray flowers are infertile.

Disk florets have tubular corollas with 5 triangular stubby lobes, 5 stamens (filaments + anthers), and a single pistil (inferior ovary + style + stigma). Corollas are to 3/16 inch long and 1/32 inch wide. The elongate, dark anthers are fused into a ring surrounding the style. With the anther ring exserted above the corolla, the style pushes through the ring moving pollen from inside the anthers to above the corolla. With pollen dispersed, anthers wither back into the corolla and the now-exserted style bifurcates and recurves to expose linear stigmatic surfaces. At anthesis, corolla lobes, anther ring and stigma are typically reddish purple, but may trend toward green. Pollen is yellow.

Each disk floret is subtended by a sharply pointed, spike-like receptacular bract, to ⅝ inch long and 1/32 wide. The green boat-shaped lower portion of the bract clasps the developing disk floret. The orange, spike-like upper portion gives the central disk a golden glow. Corollas, stamens and styles all remain below the tips of the bracts. The central disk is very prickly during anthesis and remains prickly as a dried head.

Photo 9: Ray florets surround a central disk composed of numerous disk florets. Pollen is extruded from anther rings as the style pushes through. Tips of ligules are notched or slit. Photo – July 4.
Photo 10: Green unopened disk florets can be seen toward the center of the head. Florets in early bloom bear clumps of yellow pollen pushed upward by the styles. Bifurcated, recurved stigmas are reddish purple. Upper portion of receptacular bracts is sharply pointed. Photo – July 4.
Photo 11: This involucre, 1 inch wide and ½ inch tall, is composed of various sizes of lanceolate phyllaries in several imbricated series. Phyllaries have minute, dense pubescence on their outer surface and margins. Photo – June 25.
Photo 12: This head, with a conic receptacle, is 1½ inches tall by 1⅜ inches wide. Disk florets remain below tips of the bracts. Photo June – 27.
Photo 13: Ray florets are infertile. The ligule of the lower ray floret is 2⅛ inches long and ⅜ inch wide. Single separated disk floret (lower right) is 9/16 inch long and its bract (farther right) is ⅜ inch long.

In late summer into fall, the prickly heads, stems and branches become brown to black and persist into the next growing season. The flattened, four-sided, one-seeded achenes are mostly glabrous with a concave crown tipped with several short teeth. Achenes are less than ¼ inch long. They are dispersed by birds, small mammals and surface water flow.

Photo 14: The prickly heads persist into the next growing season. Inset shows achenes. Squares = ¼ inch. Photos – August 19.

Purple Coneflower, with its large and colorful flowerheads, is an excellent perennial for a formal or informal garden. This long-blooming, mostly erect, sturdy plant prefers a sunny area with well-drained mesic soil, but will also bloom nicely in partial shade. It works well as a specimen plant, in mass plantings or as a companion plant with other summer-blooming perennials. It may self-seed too freely in some sites, but plants are easily removed (shallow rootstock). Vegetative growth, flowers and seeds provide food for many insects, birds and small mammals––plants are a favorite of Pearl Crescent butterflies and Goldfinches. Excellent for arrangements when in bloom or dried.

Photo 15: Purple Coneflower is an excellent choice for a mixed perennial bed. Photo – May 30.

Four other species of Echinacea occur in Arkansas: Pale Purple Coneflower (Echinacea pallida), Yellow Coneflower (Echinacea paradoxa var. paradoxa), Sanguine Purple Coneflower (Echinacea sanguinea), and Glade Coneflower (Echinacea simulata). Pale Purple Coneflower, Sanguine Purple Coneflower, and Glade Coneflower all have narrow leaves and strap-like pink to pale purple drooping ligules. Purple Coneflower is readily distinguished by its broad petiolate leaves and wider, more spreading ligules.

Article and photographs by ANPS member Sid Vogelpohl

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