Deer-Tongue Grass (Dichanthelium clandestinum)

Description: This perennial grass is 1½-4½' tall. The vernal phase of the culm is unbranched, while its autumnal phase branches occasionally. The culms are light green, terete, and glabrous (or nearly so). Alternate leaves occur along each culm; they are ascending to widely spreading. The leaf blades are 2-8" long and ½-1½" across; they are narrowly lanceolate, flat, and smooth along their margins, except near the culms, where the lower margins of the leaves are often ciliate. The upper blade surface is yellowish green, medium green, or dark green and lacking significant hairs, while the lower surface is similar, except it is a more pale shade of green. The bases of the blades clasp their culms. The leaf sheaths are light green, longitudinally veined, and either hairless or hairy; the upper sheaths are especially likely to be hairy.

Each vernal culm terminates in a panicle of spikelets about 2½-5" long that is exerted from the uppermost sheath; this panicle has a pyramidal shape with a central rachis and ascending to widely spreading lateral branches. The branches divide into branchlets that terminate in individual spikelets. The rachis, branches, and branchlets of the panicle are slender and slightly wiry. Individual spikelets are 2.5-3.0 mm. long, about one-half as much across, ovoid in shape, sparsely pubescent, and light green to greenish purple; each spikelet consists of a pair of glumes, a single lemma and its palea, and a perfect floret with 2 feathery stigmata and 3 stamens. The smaller glume is only one-third the length of the spikelet, while the larger glume and lemma are the same length as the spikelet. Each spikelet has about 9 fine nerves along its length. The palea is white-membranous and largely hidden from view. For the vernal culm, the blooming period occurs from early to mid-summer for about 1-2 weeks. Afterwards, the culm continues to branch, developing secondary culms in its autumnal form. The autumnal culms and their leaves have the same characteristics as the vernal culm and its leaves, except several panicles of spikelets are produced that remain inserted within their sheaths (and thus they are hidden from view). Compared to the vernal panicle, these autumnal panicles are reduced in size. Both vernal and autumnal spikelets produce ovoid grains about 2.0-2.5 mm. long. The root system is fibrous and rhizomatous. Colonies of clonal plants are often produced from the rhizomes.

Cultivation: The preference is partial sun, moist conditions, and sandy soil. In some situations, this grass can spread aggressively via its rhizomes.

Range & Habitat: The native Deer-Tongue Grass is common in southern Illinois, while in the rest of the state it is occasional (see Distribution Map). Habitats include moist depressions in rocky upland woodlands, sandy woodlands, sandy savannas, sand prairies, acidic gravelly seeps, low areas along streams, and abandoned sandy fields. This grass is more common in moist sandy habitats than elsewhere and it tolerates some disturbance.

Faunal Associations: The caterpillars of several skippers (Hesperiidae) feed on the foliage of panic grasses (Dichanthelium spp. & Panicum spp.), specifically: Hesperia sassacus (Indian Skipper), Polites themistocles (Tawny-Edged Skipper), Poanes hobomok (Hobomok Skipper), and Wallengrenia egremet (Northern Broken-Dash). The caterpillars of the moth Idioglossa miraculosa skeletonize the leaves of Deer-Tongue Grass and other panic grasses, while the caterpillars of the moth Cycloplasis panicifoliella develop blotch-mines in the leaves. Other insect feeders include the leaf beetle Chalepus bicolor, the billbug Sphenophorus callosus, the stilt bug Jalysus spinosus, the stink bugs Mormidea lugens and Oebalus pugnax, the grasshopper Arphia sulfurea, and such leafhoppers as Flexamia areolata, Polyamia herbida, and Polyamia rossi. Among vertebrate animals, the seeds of panic grasses are an important source of food to many birds, especially sparrows (see the Bird Table for a listing of these species). The seeds are also consumed by some small rodents, such as the wild House Mouse and Prairie Deer Mouse. The young foliage is palatable to many mammalian herbivores, including cattle, horses, sheep, deer, and rabbits.

Photographic Location: A moist sandy woodland and mesic sand prairie at the Indiana Dunes National Lakeshore in NW Indiana.

Comments: Deer-Tongue Grass is one of a small number of Dichanthelium spp. (cool-season panic grasses) with leaf blades that can exceed 1" in width. It starts off life as a normal cool-season panic grass, producing an exerted inflorescence during early summer when it is about 1½-2' tall. At this stage, it closely resembles Dichanthelium latifolium (Broad-Leaved Panic Grass) and similar species. However, after producing this early inflorescence, it continues to grow during the rest of the summer by forming branching culms, becoming 3-4½' tall by autumn. This additional growth makes Deer-Tongue Grass the tallest species of the numerous Dichanthelium spp. that occur in Illinois. It is also unusual in producing inflorescences that remain hidden in its autumnal sheaths – apparently the spikelets of these inflorescences are self-fertile, having abandoned cross-pollination by wind.