Crabgrass is an annual with branching, spreading stems. Its coarse, blue-green to purplish leaf blades can be smooth or hairy, depending on the species. Flower heads with several fingerlike spikes rise from narrow stems.
Crabgrass thrives in lawns mowed shorter than 2 inches, underfed lawns, and those watered frequently and lightly. Thick, deeply irrigated turf is the best control. Dig crabgrass before it seeds. Preemergence crabgrass herbicides are available; apply in spring before soil temperature reaches a steady 60 degrees Fahrenheit.