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This perennial plant is about 2½–4' tall, unbranched, and more or less erect. The culm is green, glabrous, and terete. There are up to 8 alternate leaves along the entire length of the culm. The leaf blades are up to 1½' long and ¾" (19 mm.) across; they are yellowish green to dark green, glabrous, linear in shape, flattened, furrowed along the middle, and rough-textured along their margins. These blades are arching or rather floppy. Leaf venation is parallel; on some leaf blades, there are observable cross-veins connecting the parallel veins at short intervals along the blade (septate). The sheaths are light green to green, glabrous, septate, and closed. The culm terminates in an inflorescence consisting of 1-3 (rarely 4-5) compound umbels of spikelets. There are 3 or more spreading leafy bracts underneath this inflorescence. The characteristics of the leafy bracts are similar to those of the leaf blades; they are up to 1' long and ½" (12 mm.) across. These bracts are variable in size, but at least one of them is longer than the inflorescence. A typical compound umbel produces several branches (often called 'rays') in all directions; these branches are ¼–4" in length. Each of these branches terminates in an umbellet of 5-20 spikelets; the spikelets are sessile or they have branchlets up to ½" (12 mm.) long. Both the branches and branchlets of the compound umbel are green, glabrous, stiff, and straight. At the base of each umbellet, there are one or more slender leafy bractlets; these bractlets are much smaller than the leafy bracts at the base of the compound umbel. Individual spikelets are about 3-6 mm. in length; they are ovoid in shape, consisting of overlapping scales in several series and their florets. The spikelets have a yellowish green appearance during the blooming period, but they later become brown to blackish brown. Each perfect floret has 3 stamens and an ovary with a tripartite style. The outer scale of each floret is about 1.5–2 mm. in length and ovate in shape. The blooming period occurs during early to mid-summer, lasting about 1-2 weeks. The florets are cross-pollinated by the wind. Afterwards, the florets are replaced by tiny achenes (one achene per floret). Mature achenes are about 1.0 mm. in length, ellipsoid-obovoid in shape, 3-angled, and light brown; each achene is surrounded by 5-6 bristles that are about the same length as the achene. The root system is fibrous and rhizomatous. Clonal colonies of plants are formed from the rhizomes.


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

© John Hilty

Source: Illinois Wildflowers

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