Go to DoMyOwn.com for tips and products on how to kill crabgrass. Crabgrass is one of the most common grassy weeds out there! It's tough to identify because it looks like... well, grass! Newly sprouted crabgrass can appear light green but turn dark, duller green as it grows. It grows in clumps low to the ground, and grows laterally or outward instead of upwards (like grass). hence its name! It doesn't like the shade so that's why you'll see it pop up during the Summer.