The first glume is minute, sometimes membranous or apparently absent.

1. Inflorescence an open panicle, neither spike-like nor distinctly one-sided.

D. cognata

1. Inflorescence composed of 1-sided spikes or spike-like racemes, the rachis of each winged or at least flat on the side opposite the spikelets.

2. Rachis of racemes scarcely if at all winged; culms erect, not rooting at lower nodes.

D. filiformis

2. Rachis of racemes distinctly winged (wing broader than rachis proper); culms usually ± decumbent at base, often rooting at lower nodes.

3. Spikelets ca. (1.7–) 2–2.3 mm long, the fertile lemma dark brown; second glume nearly or fully as long as the floret; sheaths and blades usually nearly or quite glabrous (except around summit of sheath).

D. ischaemum

3. Spikelets ca. 2.5–3 mm long, the fertile lemma light or dark grayish; second glume only about half as long as the floret; sheaths and usually blades ± pilose, at least toward base of plant.

D. sanguinalis

All species found in Digitaria

Digitaria cognataFALL WITCH GRASS 
Digitaria filiformisSLENDER CRAB GRASS 
Digitaria ischaemumSMOOTH CRAB GRASS 
Digitaria sanguinalisHAIRY CRAB GRASS 


MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. March 29, 2017. http://michiganflora.net/genus.aspx?id=Digitaria.