IUCN threat status:

Not evaluated

Comprehensive Description

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Description

This is a perennial plant about 2-4' tall that is either unbranched or sparingly so. The central stem is light green, grooved, and either glabrous or sparsely pubescent. The alternate compound leaves are bipinnate and up to 8" long; they have a ferny appearance. Each compound leaf has 8-12 pairs of  even-pinnate leaflets; each even-pinnate leaflet consists of 20-40 pairs of closely spaced subleaflets. Individual subleaflets are about 1/8" (3 mm.) long and about one-third as much across; they are light to medium green, lanceolate-oblong in shape, ciliate along their margins, and sessile (or nearly so). The rachises (central stalks) of the compound leaves are whitish green from fine hairs and they are grooved along their upper sides. Small white flowerheads occur individually from the axils of the upper leaves on slender peduncles up to 3" long. The peduncles are glabrous to sparsely hairy. Each flowerhead is up to ½" across and ovoid-globoid in shape; it consists of a dense head of 25-50 florets that are oriented in nearly all directions. Each floret consists of a short-campanulate calyx with 5 teeth (less than 1 mm. in length), 5 white petals (about 1 mm. in length), an ovary with a single style, and 5 strongly exerted stamens. The stamens have white filaments and pale yellow anthers. When they are fully developed, these flowerheads have a starburst appearance that is typical of compound flowers in the Mimosa family, but they appear more lumpy than spherical because the florets bloom from the bottom to the top gradually, rather than all at once. The blooming period lasts 1-2 months during the summer. There is no noticeable floral scent. Afterwards, the flowerheads are replaced by clusters of 5-15 seedpods that become dark brown at maturity. Individual seedpods are about ½" in length and two-valved; they are curved and flattened. Each seedpod splits open along its valves, releasing 2-5 seeds. The seeds are reddish brown, ovoid-reniform in shape, somewhat flattened, and shiny. This plant spreads by reseeding itself. 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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