The name "crabgrass' is used for several invasive, non-native plants that are large, coarse-leaved grasses. If not eradicated, these aggressive growers will strangle more sensitive turf grasses and form large, tangled clumps with strong, deep roots in gardens as well as lawns. Real crabgrass, also called "finger grass," is an annual, living and dying in one season. It is dull or blue-green, often with purplish stems. Perennial quack grass, or couch grass, grows taller; up to 20 inches. It is blue-green and sets rhizomes that will rise again next spring.
Apply a pre-emergent herbicide in early spring to keep seeds from germinating. Follow the label instructions for dosage.
Apply post-emergent herbicides such as MSMA, fenoxaprop-p-ethyl and quinclorac, usually available in spray form, as soon after the plant emerges as possible.
Keep the lawn mowed to the proper height and well-irrigated. Most lawn grasses should be kept less than 3 inches tall as crabgrass seed spikes grow about 6 inches tall. Keep the grass cut to impair next year's crop.
Dig out clumps of the crabgrass before the long spikes of seed begin to develop in August and September. Turn up pieces of turf or dig out long roots with a dandelion digger. Remove as much of the root as possible to prevent the plant from growing.
Repeat pre-emergent treatments each spring and keep after renegade plants.
Remove quack grass in early spring by digging it up.
Keep the lawn watered and mowed to a height of about 3 inches.
Fertilize turf grass to keep the lawn healthy. Apply two to three feedings of balanced lawn fertilizer (20-10-10) or a blend specially formulated for your soil. Follow the manufacturer's instructions for application.
Apply non-selective spray herbicides containing 2,4-D or glyphosate on stubborn or out-of-control patches. Reserve the use of grassy weed herbicides for serious infestations, as these chemicals will kill all vegetation.
About this Author
Chicago native Laura Reynolds has been writing for 40 years. She attended American University (D.C.), Northern Illinois University and University of Illinois Chicago and has a B.S. in communications (theater). Originally a secondary school communications and history teacher, she's written one book and edited several others. She has 30 years of experience as a local official, including service as a municipal judge.