Digitaria is a genus of about 300 species of grass (family Poaceae) native to tropical and warm temperate regions. Common names include crabgrass, finger-grass, and fonio. They are slender monocotyledonous annual and perennial lawn, pasture, and forage plants; some are often considered lawn pests. Digitus is the Latin word for "finger", and they are distinguished by the long, finger-like inflorescences they produce.
All crabgrasses have similar growth habits and flowering structures, but species are separated by minor differences in the flower structures and leaf pubescence. They typically have spreading stems with wide flat leaf blades that lie on the ground with the tips ascending. The inflorescence is a panicle in which the spike-like branches are arranged in digitate fashion. The spikelets are arranged in two rows on an angled or winged rachis. Each spikelet has two florets, only one of which is fertile. The first bracts at the base of the spikelets are either very minute or absent.
Crabgrass seed has a menstration germination period; if conditions are right, it can germinate throughout the growing season. Crabgrasses occur in tropical, subtropical, and temperate regions of both hemispheres.
Despite their weediness, crabgrasses do have a few redeeming qualities. The seeds, most notably those of fonio, can be toasted and ground into a flour, which can be used to make porridge or fermented to make beer. Fonio has been widely used as a staple crop in parts of Africa. It also has decent nutrient qualities as a forage for cattle.
"Crabgrass" can also refer to a garden or yard.