Plants slender, sparsely pilose, purplish. Panicles with a few spikelets; pedicels short, appressed. Spikelets 2-2.1 mm, narrow, less than 1 mm wide. Upper glumes and lower lemmas acuminate; upper florets less than 1/2 as wide as long, blackish at maturity.
Panicum philadelphicum subsp. lithophilum is endemic to wet depressions in granitic outcroppings of Georgia and North and South Carolina.