Description: This native perennial grass is 1–2½' tall and more or less erect. The culm is initially unbranched, but becomes branched later in the year. The culm is terete and either glabrous or sparsely short-pubescent. The blades of the alternate leaves are up to 5" long and 1¼" across; they are medium green, flat, and widely spreading. For the typical variety, the blades are hairless on their upper surfaces and hairless to sparsely short-pubescent on their lower surfaces. For var. molle, the blades are sparsely short-pubescent on their upper surfaces and velvety-pubescent on their lower surfaces. The leaf sheaths are hairless to sparsely short-pubescent for the typical variety, while for var. molle they are quite hairy. The nodes of both varieties have long white hairs that are downward-pointing (retrorse). The ciliate ligules at the junction of the sheaths and blades are about 1 mm. long.
The culm (and any later branches)
terminates in a panicle of spikelets up to 5" long and a little less across
(when fully exerted from its sheath). The slender branches of the panicle are
ascending, slightly curly, and glabrous. The outer branches terminates in
individual spikelets that are about 4 mm. long, 2 mm. across, and obovoid in
shape. Each spikelet consists of a pair of glumes, a sterile lemma, and a
fertile lemma enclosing a floret. The first glume is about one-third the length
of the spikelet, while the second glume and lemmas are about the same length as
the spikelet. The blooming period occurs from late spring into the summer. The
florets are wind-pollinated. Each floret is replaced by an ellipsoid grain
about 3 mm.
long.
The root system is fibrous and short-rhizomatous. Loose tufts of plants often
develop from the rhizomes. During the late summer or autumn, the flowering
culms die down and are replaced by infertile shoots that are low and
branching.
Cultivation: The
preference is dappled sunlight to light shade, dry-mesic to dry conditions, and
rocky soil.
Range & Habitat: The
typical variety of Bosc's Panic Grass is occasional in southern Illinois,
uncommon in west-central and north-central Illinois, and absent from the NE and
east-central sections of the state. It is more common than var. molle,
which is restricted to southern Illinois. Habitats include upland rocky
woodlands and savannas, rocky wooded slopes, limestone glades, and thinly
wooded bluffs. This grass can be found where either sandstone or limestone lies
close to the ground surface. In wooded areas, it benefits from occasional
wildfires.
Faunal Associations: In
the habitats where Bosc's Panic Grass occurs, a small number of insects feed on
Dichanthelium spp. They include the Hispine leaf beetle Chalepus
bicolor, the caterpillars of Poanes hobomok (Hobomok Skipper), the
Stilt bug Jalysus spinosus, and the leafhopper Polyamia herbida.
This last insect was found on Bosc's Panic Grass and other Panic grasses in
barrens at Hoosier National Forest in Indiana (Bess, 2005). The seeds of Panic
grasses are eaten by such upland gamebirds and songbirds as the Wild Turkey,
Bobwhite, and various sparrows. White-Tailed Deer and Cottontail Rabbits browse
on the foliage occasionally.
Photographic
Location: An upland rocky woodland at the Portland Arch in
west-central Indiana. The photographed plant is the downy variety of Bosc's
Panic Grass, or Dichanthelium boscii molle. A hairy node can be seen in
the upper left corner of the photograph of the leaf blades. It resembles a
hairy white ring.
Comments: This species has one of the widest leaf blades of any panic grass in Illinois (exceeding 1" across). As a result, it has a very distinctive appearance. Another species with wide leaf blades is Dichanthelium latifolium (Broad-Leaved Panic Grass); it has a similar appearance and prefers similar habitats. While Bosc's Panic Grass has nodes with long downward-pointing hairs, the nodes of Broad-Leaved Panic Grass are hairless or nearly so. The downy variety of Bosc's Panic Grass, Dichanthelium boscii molle, is similar in appearance to Dichanthelium ravenelii (Ravenel's Panic Grass), as they both have nodes with downward-pointing hairs, hairy sheaths, and leaf blades with velvety undersides. However, the leaf blades of Ravenel's Panic Grass are more narrow (¾" across or less). An older scientific name of Bosc's Panic Grass is Panicum boscii. Another common name for this species is Large-Fruited Panic Grass.