Large crabgrass is a summer annual that reproduces primarily by seeds, but can also reproduce by long, rooting tillers. It is normally mat forming, often has purple stems, and can grow to more than 3 feet in height. The leaves are pale bluish green with margins that may be rough. They are flat, sharply pointed, 1/4 to 2/5 inch wide, and 2 to 6 inches long. Large crabgrass flowers have 3 to 13 purplish finger-like spikes up to 6 inches long. They occur in spirals at the end of stout stalks during August and September. The species can be found in most warm, moist, fertile lawns in sun where turf is thin or mowed too short. It will tolerate hot, dry, compacted soils after establishment and may spread aggressively to crowd out desirable grasses.
