IUCN threat status:

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Comprehensive Description

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Description

This perennial herbaceous plant is 1½–3½' tall, branching frequently in the upper half to create a bushy appearance. The slender stems are light green, glabrous, and terete (circular in cross-section). Along the entire length of these stems, there are abundant alternate leaves that become gradually smaller in size as they ascend. These leaves are 1½–4" long and 1.5–4 mm. (less than ¼") across; they are linear in shape, entire (toothless) along their margins, medium green, glabrous (hairless), and either sessile or short-petiolate. The leaves have prominent central veins, and some of the wider leaves have pairs of lateral veins that are also visible. The upper stems terminate in clusters of flowerheads that together form a collective inflorescence that is somewhat flat-headed or dome-shaped and irregular. Within this inflorescence, clusters of 3-7 flowerheads often occur that are sessile during the bud stage, although some of them develop short pedicels while they are in bloom. The branches of these floral clusters are similar to the stems, except they are more angular and occasionally short-hairy. Small leafy bracts up to 1" long occur where these branches divide; these bracts are linear in shape. A mature flowerhead is about 3 mm. (1/8") across while in bloom, consisting of 10-12 ray florets and 4-7 disk florets. The petaloid rays of the flowerheads are short-oblong in shape, bright yellow, and ascending to widely spreading. The corollas of the disk florets are cylindrical in shape, 5-lobed, and bright yellow. At the base of each mature flowerhead, small phyllaries (floral bracts) occur in several overlapping series that are appressed together to form an involucre (a cup-shaped structure at the base of the flowerhead). For a mature flowerhead, this involucre is 4-6 mm. long and cylindrical in shape, tapering at its base. Individual phyllaries are elliptic-oblong in shape, light green to pale yellow, glabrous, and oily in appearance. The blooming period occurs from late summer to autumn, lasting about 1-2 months for a colony of plants. In the collective inflorescence of each plant, the flowerheads bloom gradually over a period of time, rather than all at once. Afterwards, the florets are replaced by achenes with small tufts of white hair; they are dispersed by the wind. These achenes are about 1 mm. long, bullet-shaped, and finely pubescent. The root system is fibrous and long-rhizomatous, often forming clonal colonies of plants. Cultivation

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Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© John Hilty

Source: Illinois Wildflowers

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