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DescriptionThis perennial wildflower is 2½-6' tall and usually unbranched, except where the inflorescence occurs. The central stem is light green to purplish green, sharply angled and sometimes narrowly winged, and hairless or nearly so; sparse short pubescence may be present above. Alternate leaves occur along the entire length of the stem, becoming smaller as they ascend upward. The basal and lower cauline leaves are 4-12" long and 1½-4" across; they are more or less obovate in shape and serrated along their margins, tapering to long winged petioles. The middle to upper cauline leaves are 2-4" long and ½-1" across; they are elliptic to oblanceolate in shape and slightly serrated to smooth along their margins. The middle to upper cauline leaves are either sessile or they have short winged petioles. The upper surface of the leaves is medium green and either hairless or covered with stiff minute hairs; the lower surface of the leaves is hairless and smooth. Sometimes the basal and lower cauline leaves become greenish yellow or wither away by the time the inflorescence appears. The central stem terminates in an open panicle of flowerheads up to 1½' long and 2' across. On a robust plant, this panicle has long primary branches that are ascending to widely spreading; they are often recurved. Each primary branch of the panicle is divided into short secondary and tertiary branches that terminate in clusters of erect flowerheads (see photo of Flowering Branch). The branches of the panicle are hairless or sparsely short pubescent. Leafy bracts up to 1" long and ½" across occur along these branches. Individual flowerheads are about 1/8" across, consisting of 5-12 ray florets that surround 5-15 disk florets. Individual ray florets have yellow corollas that are petal-like; they are pistillate and fertile. Individual disk florets have yellow corollas that are narrowly tubular with 5 spreading lobes; they are perfect and fertile. At the base of each flowerhead, there are appressed phyllaries (floral bractlets) in several series that are green and narrowly oblong in shape. The blooming period occurs from late summer into the fall for about 1-1½ months. The florets are replaced by small bullet-shaped achenes with tufts of hair. The achenes are sparsely hairy; they are distributed by the wind. The root system is fibrous and rhizomatous; sometimes a small caudex will form on an older plant. Clonal offsets often develop from the rhizomes.