n.
Any of about 300 species of grasses in the genus Digitaria , especially D. sanguinalis or the slightly shorter D. ischaemum (smooth crabgrass).
D. sanguinalis has long hairs covering its leaves and five or six spikelets; D. ischaemum has no hair and only two or three spikelets. Both are natives of Europe that became widely naturalized as weeds in North America. They and a few closely related species are very troublesome in lawns and fields. One species, Arizona cottontop ( D. californica ), is a useful forage grass in the American Southwest.
Crabgrass ( Digitaria sanguinalis )
Grant Heilman