This annual is similar to vaginiflorus and often confused. Both species are widespread on rocky base-rich sites across east-central North America and differences in ecology are not obvious. S. neglectus may be more frequent on disturbed sites such as exposed riverbanks and roadsides, but typical vaginiflorus can also be locally abundant along roads. Compared to vaginiflorus, neglectus has smaller spikelets (1.6-3 mm long versus 2.3-6 mm), with glabrous (versus strigose) lemmas, and smaller grains (usually 1.2-1.8 mm long versus 1.8-2.7 mm) that are free-falling (versus enclosed); 2n = 36 versus 54. A few Ky. colls. suggest transitions to vaginiflorus, especially if lemmas have marginal hairs (e.g. from ROWA at KNK). Potentially Intermediate plants have sometimes been name ozarkanus, which St treated as a var. of neglectus; but see notes under vaginiflorus. Before flowering, these annual species of Sporobolus can generally be distinguished from common annual species of Aristida in Ky. (dichtomota, longespica, oligantha) as follows (FNA 25): sheaths usually inflated (versus not so), the apical collars with distinct tufts of hairs to 3 mm long (versus glabrous); blades sometimes with sparse papillose-based hairs of both surfaces (versus without such hairs, although occasionally with sparse non-papillose hairs on upper surface).