IUCN threat status:

Not evaluated

Comprehensive Description

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Description

This perennial grass forms dense stands or tufted culms that are 2-5' tall. In areas where this species is more sparsely distributed, it resembles a bunchgrass, while in other areas where it is dominant, this grass forms a coarse sod. Both fertile and sterile shoots are produced. The culms are light green or straw-colored (stramineus), terete, glabrous, hollow, and unbranched. There are 5-10 alternate leaves along the entire length of each culm. The leaf blades are 4-12" long, 4-8 mm. across, and linear in shape; they tend to be widest toward the middle or lower middle. The leaf blades are ascending to widely spreading and rather floppy. The upper and lower surfaces of the leaf blades are pale green, medium green, or blue-green; they are glabrous and sometimes slightly glaucous. The leaf sheaths are pale green, longitudinally veined, glabrous, and open; they are shorter than the internodes. The ligules are white-membranous and 2-4 mm. in length; sometimes the leaves become loose at their ligules. The nodes are slightly swollen, glabrous, and dark-colored. Fertile culms terminate in panicles of single-flowered spikelets (one panicle per culm). The peduncles of these panicles are about 6-12" long. The panicles are 4-10" long and up to one-half as much across. Depending on their stage of development and the variety of this grass, these panicles can be open, loose, and narrowly pyramidal in shape (as occurs during the blooming period, particularly with var. canadensis), or they can be rather dense and contracted (as occurs before or after the blooming period, particularly with var. macouniana). The lateral branches of the panicle are up to 3" long and they can be either erect, ascending, or widely spreading below. These lateral branches subdivide into shorter secondary and tertiary branches that terminate in pale green to purplish spikelets. These branches are straight to slightly curved, but not wiry. Each spikelet has a pair of glumes, a lemma, and a floret. Depending on the variety of this grass, these spikelets vary in their size; the spikelets of var. canadensis are 3-4 mm. in length, while the spikelets of var. macouniana are 2-2.5 mm. in length. There is also a third variety, var. langsdorfi, that has spikelets 4.5-6 mm. in length, but it has not been found in Illinois thus far. The glumes are the same length as the spikelets; they are narrowly lanceolate in shape, glabrous, and convex to slightly keeled along their outer surfaces. The lemmas are slightly shorter than the glumes by up to 0.5 mm.; they are narrowly lanceolate in shape, glabrous, convex along their outer surfaces, and translucent toward their tips. Each lemma also has a tuft of white hair at its base and a delicate straight awn that extends from below the middle of the lemma to as high as its tip. The tufted hairs are the same length as the lemma or less, while extending in different directions. Each floret has 3 stamens and a pair of feathery stigmata. The blooming period occurs from early to mid-summer, lasting about 1-2 weeks for a colony of plants. The florets are cross-pollinated by the wind. Afterwards, the panicles and their spikelets become straw-colored during late summer, when the grains become mature. The tufted lemmas and their grains are dispersed by wind or water. Depending on the variety of this grass, the grains vary in size from 1.25-2 mm. in length; they are narrowly ellipsoid-oblongoid, light brown, glabrous, and very light in weight. The root system is fibrous and rhizomatous. Clonal offsets develop from the rhizomes. This grass occasionally forms large colonies at favorable sites.

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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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