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Description

This perennial wildflower is 3-8' tall, branching sparingly. The large hollow stems are pale purple to dark purple, terete, glabrous, and often glaucous. Alternate compound leaves occur along the stems, primarily along the lower-half of each plant. The compound leaves are ½-2' long, ½-2' across, and widest at their bases. The structure of the compound leaves is bipinnate with 3-5 leaflets or subleaflets per division. The subleaflets are ¾-4½" long and ½-2½" across; they are more or less ovate in shape and their margins are serrated. Some subleaflets are shallowly to deeply cleft into lobes. The upper surface of the subleaflets is medium to dark green and glabrous, while the lower surface is pale or whitish green and glabrous. The subleaflets are either sessile or they have short petioles; they often have winged extensions at their bases that join the branches of the rachis. The petioles are long, stout, and conspicuously sheathed at their bases; both the petioles and their sheaths are green to light purple to dark purple, glabrous, and often glaucous. The upper stems terminate in one or more compound umbels of flowers spanning 3-9" across; they are globoid in shape. Sometimes the peduncle of a compound umbel will branch and terminate in another compound umbel. Each compound umbel has 15-40 rays (floral branches) that terminate in small umbellets. Each umbellet has numerous greenish white to pale yellow flowers on pedicels about ½" in length. Each flower is up to ¼" across, consisting of 5 petals with incurved tips, a light green calyx without significant lobes, 5 stamens, and a pistil with a divided style. The blooming period occurs from late spring to early summer and lasts about 3 weeks. Afterwards, the flowers are replaced by dry seed-like fruits (consisting of double achenes). The fruits are 5-8 mm. in length, oblongoid-ovoid in shape, and slightly flattened; each side of the fruit has 3 longitudinal ridges. Immature fruits are greenish yellow, turning brown at maturity. Each achene has a pair of lateral wings along its main body; it is convex and ridged on one side, while the other side is flat. The root system consists of a short stout taproot.

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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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