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How to Eradicate Annual & Perennial Crabgrass

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How to Eradicate Annual & Perennial Crabgrass

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Overview

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.

Annual Grass

Step 1

Apply a pre-emergent herbicide in early spring to keep seeds from germinating. Follow the label instructions for dosage.

Step 2

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.

Step 3

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.

Step 4

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.

Step 5

Repeat pre-emergent treatments each spring and keep after renegade plants.

Perennial Grass

Step 1

Remove quack grass in early spring by digging it up.

Step 2

Keep the lawn watered and mowed to a height of about 3 inches.

Step 3

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.

Step 4

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.

Tips and Warnings

  • Annual and perennial grasses send out rhizomes, special roots that run just under the soil surface and pop up new plants. When digging out plants, don't neglect the offspring. Don't fertilize during the heat of summer. Most turf grasses are dormant during this period; the only grasses that benefit are the weeds. Quack grass is more tolerant of mowing than crabgrass. Its seed spikes are about 6 inches long and it favors dry areas and thin lawns. Once crabgrass sets seed, there is nothing that can be done to kill it until the next spring.

Things You'll Need

  • Dandelion digger
  • Garden spade
  • Pre-emergent herbicide
  • Post-emergent herbicide
  • Fertilizer spreader
  • Herbicide sprayer

References

  • University of Illinois Turf Grass Program: Crabgrass
  • University of Minnesota Extension: Quackgrass Management
  • Colorado State University Extension: Control of Grassy Weeds in Lawns

Who Can Help

  • Colorado State University: Identification and Management of Perennial Weedy Grasses
  • University of Illinois Extension: Managing Grass Weeds in Lawns
  • Iowa State University Extension: Using Biological Control Strategies for Turf
Keywords: annual crabgrass, perennial crabgrass, quack grass, invasive grasses

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.

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