Comprehensive Description

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This grass is a summer annual about ¾–3' tall that is usually tufted at the base, sending up multiple leafy culms from the same crown, otherwise it is unbranched or sparingly so. The culms are light green, terete, and nearly hairless to hairy. The alternate leaves are more common toward the base of the culms. Their blades are up to 10" long, up to 16 mm. across, and rather floppy; they are light to medium green and variably hairy, often becoming rather ragged in appearance with age. The upper blade surface is hairless to densely covered with appressed hairs, while the lower blade surface has a few scattered hairs along the central vein, or it is moderately to densely covered with long spreading hairs. The leaf sheaths are light green to reddish green, longitudinally veined, and densely covered with long spreading hairs; they are wrapped rather loosely around the culms. The ligules are short-hairy. Each culm terminates in a strongly branched panicle of solitary spikelets that is little-exerted from the uppermost leaf. Immature panicles are funnel-shaped with a dense concentration of branchlets and spikelets. Mature panicles are globular-ovoid in outline and airy in appearance from the widely spreading branchlets; they are up to 1½' long and 1' across. Mature panicles often comprise about one-half of the length of the entire plant. The light green rachis (central axis) of the panicle is hairy, particularly at the swollen nodes where the primary branches occur. These branches divide into slender branchlets; they are light green, rather wiry, stiff, and scabrous (rough-textured). The branchlets ultimately terminate in solitary spikelets with short pedicels. The spikelets of the typical variety of Witch Grass are about 2.0–2.5 mm. long, ellipsoid-ovoid in shape, and hairless; they taper gradually to beak-like tips. The scales of each spikelet consist of a short glume, a long glume (that looks like a lemma), and a single fertile lemma. The short glume is about one-third of the length of the spikelet, while the long glume is the same length as the spikelet and the lemma is a little shorter than the spikelet. The short glume is broadly ovate in shape; it often becomes pale purple, otherwise the scales of the spikelet are light green. The blooming period occurs during late summer and early fall, lasting about 2 weeks for a colony of plants. The perfect florets of the lemmas are either cross-pollinated by the wind or they are self-fertile. Shortly afterwards, the panicles and their spikelets become light tan. The entire panicle can detach from the plant and roll across the ground like a tumbleweed, distributing the grains. Each spikelet produces a single grain. The grains are about 1.5 mm. long, broadly ellipsoid in shape, slightly flattened, and pointed at both ends. The root system is fibrous. This grass spreads by reseeding itself. It often occurs as widely scattered plants in a given habitat, or it may form dense colonies that are dominated by the airy panicles.


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

© John Hilty

Source: Illinois Wildflowers

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