Crabgrass is a summer annual grass with wider blades and a lighter green color than bluegrass. It is low growing, prostrate, and often has reddish-purple stems. It forms seedheads below mowing height. The seedheads are composed of slender, fingerlike spikes.
Crabgrass is less prevalent when turf has good density. Increase density using cultural practices detailed in CSU Fact Sheet 7.202, Lawn care. In particular, mowing too low promotes crabgrass seed germination. Maintain mowing heights of 2.5 - 3 inches.
Crabgrass seedling Crabgrass seedheads
A pre-emergent herbicide (benefin + trifluralin, dithiopyr, DCPA, oxadiazon, pendimethalin, or prodiamine) applied correctly and at the proper time should provide control. Do not use a pre-emergent herbicide on a newly seeded or sodded lawn or when overseeding a lawn.
Fenoxaprop and other post-emergent "crabgrass killer" (MSMA, DSMA, MAMA) sprays are not effective unless crabgrass plants are immature, young seedlings. Always read the label before applying any pesticide.
Photographs courtesy of Judy Sedbrook.
© CSU/Denver County Extension Master Gardener 2010
888 E. Iliff Avenue, Denver, CO 80210
Date last revised: 01/05/2010