Description: This native perennial grass is 3-6' tall and more or less erect; it usually grows in large bunches. The culms are light to medium green, terete, glabrous, and fairly stout; each culm has several alternate leaves that span most of its length underneath the inflorescence. The leaf blades are up to 2/3" (15 mm.) across and 2' long; they are usually medium green (less often blue and glaucous), hairless or mostly hairless, and ascending to widely spreading. The leaf sheaths are about the same color as the blades and hairless; they are open at the mouth. Each ligule has a band of white hairs, while the nodes are swollen and often dark-colored.
The culm terminates in an inflorescence
about 8-20" long and half as much across. This inflorescence is an airy panicle
of spikelets; is broader toward the bottom than the top (pyramidal or conical).
The slender branches of the panicle are ascending to spreading and fairly
straight. Each branch terminates in a small spikelet about 4-5 mm. long that is
ellipsoid or narrowly ovoid in shape. The spikelets are initially light reddish
purple, but they later become light tan. Each spikelet has a pair of glumes, a
single fertile lemma, and a floret. The first glume is about two-thirds the
length of the spikelet, while the remaining glume and lemma are the same length
as the spikelet. The first glume gradually tapers to a long tip. The blooming
period occurs during mid-summer. Pollination of the florets is by wind. The
floret of each spikelet is replaced by a grain that is 2-3 mm. long; this grain
is ovoid-oblong in shape and somewhat flattened on one side. The root system is
fibrous and rhizomatous; the fibrous roots can penetrate more than 10 ft. in
the ground. Reproduction is by seed and vegetatively through
rhizomes.
Cultivation: The
preference is partial to full sunlight, moist to mesic conditions, and deep
fertile soil. However, this robust grass can tolerate practically any kind of
soil and it will adapt to drier conditions. This grass can spread aggressively,
therefore it should not be overplanted.
Range
& Habitat: Switch Grass is a common plant that has been found in
most areas of Illinois, except for a few counties in the southern half of the
state (see
Distribution
Map). Habitats include black soil prairies, clay prairies, sand prairies,
typical savannas and sandy savannas, open woodlands, rocky bluffs, sand dunes,
marshes and sandy pannes, rocky banks of rivers, prairie restorations, areas
along railroads and roadsides, and abandoned fields. Because of its
above-average tolerance of salt, this species can become the dominant grass
along little-mowed roadsides where salt is applied during the winter. Like
other prairie species, this native grass recovers readily from occasional
wildfires.
Faunal
Associations: Various insects feed on the foliage of Switch Grass
and other Panicum spp. (Panic Grasses). These include the caterpillars
of skippers Atrytone logan (Delaware Skipper), Hesperia leonardus
(Leonard's Skipper), Hesperia sassacus (Indian Skipper), Poanes
hobomok (Hobomok Skipper), Polites themistocles (Tawny-Edged
Skipper), and Wallengrenia egremet (Northern Broken-Dash). The
caterpillars of the moth Cycloplasis panicifoliella are leaf-miners of
Panic Grasses. Leafhoppers that feed on Switch Grass include various
Flexamia spp. and Graminella spp. The seeds of Switch Grass are
eaten by a variety of birds, including wetland birds, upland gamebirds, and
granivorous songbirds (see the Bird Table for a listing of these species). When Switch Grass
occurs near marshes, it is a food plant of the Muskrat. The young foliage of
this grass is eaten by hoofed mammalian herbivores, including deer, horses,
cattle, sheep, and goats. Because Switch Grass remains upright during the
winter and often forms large clumps, it provides good cover for various birds
and small mammals during this time of year.
Photographic Location: A wildflower garden at
Crystal Lake Park in Urbana, Illinois. The plants in the upper photograph are
leaning sideways toward the sunlight because they were growing at the edge of
the garden. Normally, this grass is more erect.
Comments: This is one of the dominant grasses of the
tallgrass prairie. Like the other dominant grasses, Switchgrass has a C4
metabolism that enables it to withstand summer weather that is hot and dry.
This is the tallest and most robust Panicum sp. (Panic Grass) in
Illinois, and it can be distinguished from most of the others by its size. One
common species with a similar appearance that can become almost as large is
Panicum dichotomiflorum (Fall Panicum). This latter species is hairless
or mostly hairless like Switch Grass, but its spikelets are smaller in size
(2-3 mm.) than those of Switch Grass. Furthermore, the first glumes of Fall
Panicum are about one-fourth the length of their spikelets, while the first
glumes of Switch Grass are about two-thirds the length of their spikelets.
Other tall-growing Panic Grasses have hairier sheaths and/or leaves, and they
have smaller spikelets than Switch Grass as well. With the increase in the
price of gasoline, Switch Grass is being evaluated as a possible source of
alcohol, which would be used as an alternative fuel. Apparently, it can produce
more alcohol per acre than corn and doesn't require replanting in the spring
because of its perennial habit.