IUCN threat status:

Not evaluated

Comprehensive Description

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Description

This perennial wildflower is 3-9' tall and largely unbranched, except for some lateral ascending stems along the upper one-third of its length. The central stem is dark purple to pale purplish white, stout, terete, glabrous, and glaucous; the interior of the central stem is mostly hollow. The lateral stems are similar, except they are more narrow. Whorls of 4-7 leaves (usually 5-6) occur at intervals along the central stem; whorls of smaller leaves also occur along some of the lateral stems. Individual leaves are up to 9" long and 3" across; they are elliptic in shape and crenate-serrate along their margins. The upper leaf surface is medium green and glabrous; it is creased along the veins. The lower leaf surface is pale green and mostly glabrous, except for hairs along the lower sides of the veins. The petioles are up to ½" long, pale purple to dark purple, and stout. The central stem terminates in a panicle of flowerheads up to 1½' long and 1' across; the upper lateral stems often terminate in panicles of flowerheads as well, except they are smaller in size. Individual panicles are rather open and dome-shaped at the top; they vary in color from pale pink-lavender to deep rosy pink. Individual flowerheads are about 9 mm. (1/3") long and 3 mm. (1/8") across, consisting of 5-7 disk florets and no ray florets. Each disk floret consists of a narrowly cylindrical corolla with 5 upright lobes, 5 inserted stamens, and a pistil with an exserted bifurcated style. The corolla is pink-lavender to rosy pink. At the base of each flowerhead, there are overlapping bracts (phyllaries) that are appressed together in several series. These bracts are usually linear-oblong, white with pink tints to light pink, and glabrous. The branches of each panicle are widely spreading to ascending; they are usually dark purple and finely pubescent. The blooming period occurs from mid-summer to early fall and lasts about 1 month. The flowerheads are often mildly fragrant. Afterwards, the disk florets are replaced by small bullet-shaped achenes (about 3 mm. long) with tufts of bristly hair. They are distributed by the wind. The root system is mostly fibrous, although sometimes rhizomes are produced.

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© John Hilty

Source: Illinois Wildflowers

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