Annual herb, tufted 8 cm - 1 m tall Leaves: often crowded at the base. Sheaths usually longer than internodes, rounded, hairy (hairs to 5 mm long and bumpy-based). Ligules 0.5 - 1.5 mm long, membranous. Blades upright to ascending, greenish or purplish, 3 - 30 cm long, 2 - 12 mm wide, linear with a truncate (cut straight across) to nearly heart-shaped base and pointed tip, flat, parallel-veined, stiff-hairy to sparsely soft-hairy, marginally fringed with hairs at the base. Inflorescence: a branched arrangement of spikelets (panicle), diffuse, 7 - 27 cm long, 4 - 24 cm wide, one-fourth to one-third as long as the plant, with spreading primary branches and appressed to diverging secondary branches. Secondary branches with one to four spikelets. Fruit: a caryopsis, indehiscent, enclosed within the persistent lemma and palea. Culm: upright to decumbent, unbranched to many-branched, 8 cm - 1 m long, about 1 mm wide, round in cross-section, hairy (hairs bumpy-based). Nodes sparsely to densely soft-hairy. Spikelets: green, 1.5 - 2.5 mm long, about 0.5 mm wide, lance-shaped to ellipsoid. Glumes: unequal, herbaceous. Lower glumes 0.5 - 1 mm long, less than half as long as spikelets, truncate (cut straight across) to pointed at the apex, three- to four-veined. Upper glumes 1.5 - 2 mm long, seven-veined. Lemmas:: Lower lemmas similar to upper glumes, 1.5 - 2 mm long, seven- to nine-veined, keeled. Upper lemmas shiny, with rolled-up margins on the upper surface. Paleas:: Lower paleas absent. Upper paleas longitudinally lined. Florets:: Lower florets sterile. Upper florets bisexual, usually dark brown, about 1.5 mm long, under 0.5 mm wide, pointed and minutely bumpy at the apex. Anthers three. Stigmas red.
Similar species: No information at this time.
Flowering: July to October
Habitat and ecology: Rare in the Chicago Region. It is a plant of limestone pavements and outcrops.
Occurence in the Chicago region: native
Etymology: Panicum comes from the Latin word panis, meaning bread, or panus, meaning "ear of millet." Philadelphicum means "of or from Philadelphia."
Slender annual 1-5 dm, erect or rarely decumbent, branched from the base; blades usually yellowish-green, 3-8 mm, wide; pedicel well exsert; panicle ovoid, ca a third as long as the entire plant; spikelets tending to be paired at the ends of capillary branches; axillary pulvini short-villous to glabrous; spikelets ovoid to ellipsoid, 1.6-2.4 mm, the first glume obtuse or acute, two-fifths as long as the abruptly acuminate second glume and sterile lemma; fr plump, becoming blackish; margins of the lemma barely inrolled, the exposed part of the palea half to three-quarters as wide as the fr; 2n=18. Dry soil and sand fields; N.S. and N.Y. to Minn., s. to Ga. and Tex. (P. tuckermanii, the form, chiefly northern, with the axillary pulvini glabrous)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.