Woolly Panic Grass
Dichanthelium acuminatum fasciculatum
Grass family (Poaceae)

Description: This perennial grass is tufted at the base, sending out multiple culms that are erect to spreading and up to 2' long. The culms are green to reddish green and terete, branching occasionally to produce lateral stems. The nodes of these culms have long white hairs; sometimes the culms are reddish near the nodes. Alternate leaves occur along the entire length of each culm. The leaf blades are up to 4" long and 10 mm. across; they are narrowly lanceolate, green, and flat. The upper blade surface is hairless or sparsely covered with short white hairs, while the lower blade surface is more or less hairy. The lower margins of leaf blades are often ciliate with long white hairs. The leaf sheaths are green, longitudinally veined, and heavily covered with long white hairs. Each culm terminates in a panicle of spikelets up to 4" long and about one-half as broad. The rachis of the panicle has long spreading hairs, particularly along its lower half. The slender branches and branchlets of the panicle are usually glabrous, slightly wiry, and spreading to ascending, ultimately terminating in pedicellate one-flowered spikelets. These spikelets are 1.5–2 mm. long, green to purple, conspicuously pubescent, and ovoid to obovoid in shape; they later become tan.

The smaller glumes are about one-fourth to one-third the length of the spikelets, while the lemmas and larger glumes are about the same length as the spikelets. The lateral stems of the culms often terminate in panicles of spikelets as well, although they are smaller in size. The primary blooming period typically occurs during early summer, lasting about 1-2 weeks for a colony of plants. The florets of the spikelets are cross-pollinated by the wind. After the vernal phase of development, this grass, like other Dichanthelium spp., dies down during mid- to late summer. During the autumnal phase of development, this grass regenerates itself and forms a low rosette of spreading culms and leaves. Sometimes panicles of spikelets are formed, and a second blooming period may occur during the autumn. Each spikelet produces a single grain; the grains are about 1.5 mm. long, broadly ellipsoid, and slightly flattened. The root system is fibrous. This grass spreads by reseeding itself.

Cultivation: The preference is light shade to full sun and moist to dry conditions. Different kinds of soil are tolerated, including those containing loam, clay-loam, rocky material, and sand. This grass has a tendency to die out if it competes with taller ground vegetation.

Range & Habitat: Woolly Panic Grass occurs in all counties of Illinois (see Distribution Map), where it is native and common. Habitats include openings in upland woodlands, openings in sandy woodlands, typical savannas and sandy savannas, disturbed meadows in wooded areas, disturbed areas of mesic to dry prairies, sand prairies, sandstone glades, thinly wooded bluffs, powerline clearances in wooded areas, and old fields. Less often, this grass can be found in open wetland areas, such as sandflats, but this is unusual. Woolly Panic Grass prefers disturbed areas with reduced ground vegetation and it has low fidelity to any particular habitat.

Faunal Associations: The caterpillars of several skippers feed on the foliage of panic grasses (Panicum spp. and Dichanthelium spp.), including Hesperia sassacus (Indian Skipper), Poanes hobomok (Hobomok Skipper), Polites themistocles (Tawny-edged Skipper), and Wallengrenia egremet (Northern Broken-Dash). Other insect species that feed on these grasses include leaf-mining larvae of moths (Elachista spp.), the leaf beetle Chalepus bicolor, larvae of the gall fly Calamomyia panici, the stilt bug Jalysus spinosus, plant bugs (Collaria spp.), the stink bug Mormidea lugens, the leafhopper Polyamia rossi, Prociphilus erigeronensis (Erigeron Root Aphid) and other aphids, and Arphia sulphurea (Sulphur-winged Grasshopper); see the Insect Table for more information. The seeds of panic grasses are an important source of food to many birds, particularly upland gamebirds and granivorous songbirds (see the Bird Table for a listing of these species). Panic Grasses are eaten occasionally by the Cottontail Rabbit and hoofed mammalian herbivores (primarily livestock); the foliage of these grasses is palatable while it is young (Martin et al., 1951/1961).

Photographic Location: A powerline clearance at Busey Woods in Urbana, Illinois.

Comments: This is one of the more common panic grasses (Dichanthelium spp.) in Illinois. It used to be referred to as Panicum lanuginosum fasciculatum, however the shorter panic grasses have been separated into their own genus. These panic grasses bloom during the late spring or early summer, die down during mid- to late summer, and develop low rosettes during the fall, at which time they may bloom again. Those grasses remaining in the Panicum genus tend to be taller warm-season grasses that bloom from mid-summer to the early fall, after which they die down and become dormant during the winter. There are several varieties of Woolly Panic Grass (Dichanthelium acuminatum) that are difficult to distinguish and sometimes intergrade in the field; see Mohlenbrock (2001) for a description of these varieties. The variety that has been described here, var. fasciculatum, is the most common of these varieties in Illinois. Woolly Panic Grass can be identified by its pubescent spikelets, the hairiness of the lower rachis in the inflorescence, and the length of its spikelets (1.5–2.0 mm.). Other panic grasses may have hairless spikelets, a hairless rachis in the inflorescence, and spikelets that are either longer or shorter in length. Sometimes the relative hairiness of the sheaths and leaf blades (both upper and lower surfaces) can be used to distinguish different varieties or species of panic grasses.