IUCN threat status:

Not evaluated

Comprehensive Description

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Description

This perennial plant is about 1-3' tall; it is usually unbranched, otherwise branching sparingly. The green or reddish central stem is four-angled and ridged; it may be hairless or slightly pubescent. This plant has a tendency to sprawl in the absence of supportive vegetation. The opposite leaves are spaced somewhat widely along the stems; they are sessile or short-petioled. The leaf blades are up to 3" long and ¾" across; they are lanceolate, ovate-lanceolate, or elliptic-lanceolate in shape. The lower leaves are narrowly lobed or pinnatifid toward their bases, while the upper leaves are coarsely dentate all along their margins. The leaves are hairless, except for a few hairs along the central veins of their undersides. Dense axillary whorls of white flowers occur where pairs of middle to upper leaves join the stem. Individual flowers are about 1/8" (2-3 mm.) in length. Each flower has a white short-tubular corolla with 4 spreading lobes, a light green calyx with 5 teeth, 2 exerted stamens, and a pistil. The calyx teeth are narrowly triangular and about twice as long as they are across. The corolla is only a little longer than the teeth of the calyx. The blooming period occurs from mid-summer to fall, lasting about 2 months. Neither the foliage nor the flowers have any noticeable fragrance. Afterwards, the flowers are replaced by nutlets in groups of 4 that are shorter than the calyx. These nutlets are broad and flat at the top, becoming rounded and more narrow along 3 angles toward the bottom; they have smooth surfaces. The root system is rhizomatous, but lacks tubers. Colonies of clonal plants are often formed from the rhizomes.

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© John Hilty

Source: Illinois Wildflowers

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