Panicum capillare capillare
Grass family (Poaceae)
Description: This native grass is a summer annual about 1-3' tall that is usually tufted at the base, sending up multiple culms, otherwise it is little-branched. The culms are 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, 2/3" across, and rather floppy; they are green and variably hairy, often becoming rather ragged in appearance with age. The upper surface of each blade can be hairless to densely covered with appressed hairs, while the lower surface can have a few scattered hairs along the central vein to densely covered with with long spreading hairs. The leaf sheaths are light green to pale reddish green, finely ribbed, and densely covered with long spreading hairs. Each culm terminates in a strongly branched panicle of 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 ovoid-globular and airy in appearance from the widely spreading branchlets; they are up to 1½' long and 1' across. Mature panicles often comprise one-half the length of the entire plant. The central axis of the panicle is hairy, particularly at the swollen nodes where the primary branchlets occur. The slender branchlets are rather wiry, stiff, and mostly hairless. Each branchlet terminates in a single spikelet. Each spikelet is about 2.02.5 mm. long, narrowly ovoid, and hairless; it has a short beak at its apex. The scales of the spikelet consist of a short glume, a long glume (that looks like a lemma), and a single lemma. The short glume is about 1/3 the length of the spikelet, while the long glume and lemma are the same length as the spikelet. The short glume is broadly lanceolate; it often becomes pale purple, otherwise the scales of the spikelet are light green. The blooming period occurs during late summer and early fall. 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 about 1.5 mm. long. The grains are ovoid and rather flattened, each one tapering to a point 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.
Cultivation: The preference is full sun, mesic to dry conditions, and a barren soil that is sandy or gravelly. The fertility of the soil and moisture levels influence the size of individual plants. Alkaline soil is tolerated quite well.
Range & Habitat: Witch Grass is common throughout Illinois; it has been observed in most counties (see Distribution Map). Habitats include disturbed areas of prairies (including sand and gravel prairies), limestone and sandstone glades, chert and granite glades, gravelly bars near rivers, gravelly areas along railroads (including the limestone ballast), fields, and barren waste areas. In Illinois, this grass is a railroad weed primarily. It prefers disturbed areas.
Faunal Associations: The caterpillars of several skippers feed on the foliage of Panicum spp. (Panic Grasses), including Hesperia sassacus (Indian Skipper), Poanes hobomok (Hobomok Skipper), Polites themistocles (Tawny-Edged Skipper), and Wallengrenia egremet (Northern Broken-Dash). The seeds of Panic Grasses are an important source of food to upland gamebirds and granivorous songbirds (see Bird Table). The foliage is occasionally eaten by rabbits and hoofed mammalian herbivores while it is young and tender.
Photographic Location: A gravelly area along a railroad in Urbana, Illinois. The inflorescence in the upper photograph is immature.
Comments: Witch Grass is a member of a small group of Panicum spp. (Panic Grasses) that are summer annuals with widely spreading panicles of small spikelets. They are similar in appearance to each other and can be difficult to distinguish. Witch Grass differs from another common species, Panicum dichotomiflorum (Fall Panicum) by its hairy sheaths; the latter has hairless sheaths. Another species, Panicum milaceum (Broomcorn Millet), has been introduced from Eurasia. It has longer spikelets (about 5.0 mm. in length) and the branchlets of its inflorescence have a tendency to droop. In contrast, the branchlets of Witch Grass are rather stiff and straight. A less common variety of Witch Grass, Panicum capillare occidentale, has longer spikelets (about 2.53.5 mm. in length) and a panicle that is more exerted from the uppermost leaf. Two other species, Panicum philadelphicum and Panicum gattingeri, are sometimes considered varieties of Witch Grass as well. They have more narrow leaf blades (1/3" or less) and differ in other minor characteristics. See Mohlenbrock (1973/2001) for a discussion of these differences.