Panicum rigidulum Bosc ex Nees
Red Top Panicum
Natural range: Broadly distributed in the eastern U.S., also in western states, and beyond
Habitat: Varied, usually moist
Florida status: Native
Recognition: Spikelets with variable reddish cast. The inflorescence emerging congested and upright, then the branches spreading. Fertile lemmas with a tiny tuft of apical hairs. Midvein of the leaf is white (or whitish).
See also the rare and putatively synonymous P. abscissum of wet habitats, but this species, if recognized as distinct, has broadly auriculate leaf sheaths and does not have hairs on the tip of the fertile lemma.
Similar to P. anceps and related to it. Both have the hair tuft on the upper lemma. Panicum rigidulum differs from P. anceps by not having a scaly chicken-foot rhizome, by having the leaf sheaths sharp-creased, ligules 0.3-3 mm (vs. < 0.5 mm), spikelets often tending to be smaller (1.3)1.6-3.8 mm ( vs. > 2.3 in P. anceps) and not slightly curled (i.e., not falcate).
Differs from P. longifolium by having a membranous (not ciliate) ligule.