Witch Grass is a member of a small group of Panicum spp. (Panic Grasses) that are summer annuals with widely spreading panicles of small spikelets. They are similar in appearance to each other and can be difficult to distinguish. Witch Grass differs from another common species, Panicum dichotomiflorum (Fall Panicum) by its hairy sheaths; the latter has hairless sheaths. Another species, Panicum milaceum (Broomcorn Millet), has been introduced from Eurasia. It has longer spikelets (about 5.0 mm. in length) and the branchlets of its inflorescence have a tendency to droop. In contrast, the branchlets of Witch Grass are rather stiff and straight. A less common variety of Witch Grass, Panicum capillare occidentale, has longer spikelets (about 2.5–3.5 mm. in length) and a panicle that is more exerted from the uppermost leaf. Two other species, Panicum philadelphicum and Panicum gattingeri, are sometimes considered varieties of Witch Grass as well. They have more narrow leaf blades (1/3" or less) and differ in other minor characteristics. See Mohlenbrock (1973/2001) for a discussion of these differences.