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 2.0–2.5 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
2.5–3.5 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.