Large crabgrass is very similar to smooth crabgrass. However, it has hairs on its leaves and sheaths. It has tall branches that emerge from the center and feature seed head spikelets. It prefers thin turfgrass and grows in a thick patch, stretching out like a crab as it emerges from the soil.
Growing a thick, healthy lawn is one way to keep crabgrass from filling in the gaps in the lawn. In the spring, use a pre-emergent herbicide with dithiopyr to prevent crabgrass weeds from growing. Postemergent herbicides with the same ingredient also work well at killing and controlling this weed.