Perennial herb, tufted 40 cm - 1.5 m tall Leaves: alternate, two-ranked. Sheaths keeled or compressed, with a hairless throat (or sparsely soft-hairy on the sides). Ligules to 1 mm long, membranous, erose (appearing unevenly cut or incised) along the margins or fringed with hairs. Blades 8 cm - 0.5 m long, 5 - 12 mm wide, flat, parallel-veined, smooth or minutely rough. Inflorescence: a dense, branched arrangement of spikelets (panicle), terminal and axillary, 9 - 40 cm long, one-third to three-fourths as wide as long, with many spikelets. Fruit: a caryopsis, indehiscent, enclosed within the persistent lemma and palea. Culm: stout, 40 cm - 1.5 m long, compressed. Spikelets: crowded, short-stalked (with one to several hairs near the apex), green or tinged purple, 1.5 - 2.5 mm long, over 0.5 mm wide, lance-shaped. Glumes: unequal, herbaceous. Lower glumes to three-fourths as long as spikelets, three-veined, midveins keeled. Upper glumes nearly equal to or slightly longer than lower lemmas, often spreading slightly apart at the apex, minutely rough at the apex, five-veined, midvein keeled. Lemmas:: Lower lemmas similar to and nearly equal to or slightly shorter than upper glumes, often spreading slightly apart at the apex, minutely rough at the apex, five-veined, midvein keeled. Upper lemmas clasping upper paleas for all their length, stiff, thick, shiny, with rolled-up margins on the upper surface. Paleas:: Lower paleas small, to two-thirds as long as lower lemmas, transparent. Upper paleas longitudinally lined. Florets:: Lower florets sterile. Upper florets bisexual, sometimes stalked, 1.5 - 2 mm long, 0.5 - 1 mm wide, to three-fourths as long as spikelets, pointed at the apex, shiny, with a tuft of minute hairs at the apex. Anthers three. Stigmas red.
Similar species: No information at this time.
Flowering: mid-July to late August
Habitat and ecology: Local in sandy soil and often found in ditches.
Occurence in the Chicago region: native
Etymology: Panicum comes from the Latin word panis, meaning bread, or panus, meaning "ear of millet." Rigidulum means "somewhat rigid."
Author: The Morton Arboretum
From Flora of Indiana (1940) by Charles C. Deam
Infrequent to frequent in the sandy areas of the northwestern part of the state; more frequent in the southwestern part, where it usually grows in large clumps in hard, white clay soil in dried-up swamps and on the borders of streams, lakes, ditches, sloughs, and old canals. In our northern counties it grows in wet, sandy, or muddy soil.