The Homeowners Column

The Homeowners Column

Controlling Crabgrass In the Lawn

Photo of Sandra Mason

Sandra Mason
Extension Educator, Horticulture
slmason@illinois.edu

One of the most popular questions I hear this time of year is, "When do I
apply crabgrass control to my yard?" The question seems to be as commonplace as, "What time is dinner?" However not all lawns need crabgrass control and not all grassy weeds are crabgrass.

Crabgrass is an annual weed and usually appears near sidewalks and driveways where the turfgrass has been killed due to car or foot traffic. Some people take the "at least it's green" attitude when dealing with crabgrass and other lawn weeds and learn to live with it. First be sure the grassy weed you have is indeed crabgrass. If the same plant comes back every year, then it is one of the perennial grassy weeds such as nimblewill, tall fescue or quackgrass. If it is greening up right now, then it is not crabgrass.

Traditional crabgrass herbicides will not control these perennial weeds
adequately.

If an herbicide is desired to control crabgrass, it is usually a preemergent
weedkiller that controls the seed emergence. Timing is crucial as the
herbicide must be applied before the weed seedlings emerge. In central
Illinois mid to late April is the time to apply crabgrass control.

Preemergent control should be applied as the soil temperatures reach 50
degrees for three consecutive days. This year that may occur fairly early.
It should not be applied too early or late season control may be lost. Some
herbicides may be reapplied later in the season for continued control. Read
the label for timing and rates.

April is also the time for establishing a lawn by seed. However do not use
preemergent herbicide control if you also plan on reseeding the lawn this
spring. The herbicide will also keep the lawn grass from germinating. The
herbicide siduron sold as Tupersan is the only preemergent that can be used
at the same time as seeding. Be sure to read and follow all label directions. When applying herbicides, consider spot treating where the weed is a problem rather than treating the entire lawn. It will save you time, money and effort and will be healthier for the environment. The best defense against weeds, insects and disease is maintaining a healthy, dense grass by proper fertilizing, watering, mowing and cultivation. Any bare soil will invite weeds. Spring is a good time to evaluate the lawn and start some good management practices.

The first step in lawn improvement is determining the cause of decline.
The smorgasbord of reasons besides improper management practices include: environmental stress from drought, heat and cold; weed, insect and disease problems; excessive thatch; poor growing conditions such as too much shade or poor soil conditions; and just plain old neglect and abuse. Of course more than one of these conditions can exist.

Once the cause has been determined, select the best improvement program
considering the present condition and expected level of lawn quality. Turf
improvement options include:

  1. starting sound cultural management practices
  2. renovating the turf by planting into the existing live or dead vegetation
  3. totally reestablishing the lawn.

Lawns, which respond best to management improvements, should have some basics such as acceptable grass species for area and use, adequate density of grass plants, acceptable soil conditions, adequate light and any grassy perennial weeds in small quantities.

If improving management practices isn't enough, then consider replanting the lawn. Select the proper grass species for your use, environment and
management level. All grass seed is not the same and it is not just a matter of sun or shade mixes.

For more information on lawns contact the Champaign Extension Unit for
Horticulture Fact Sheets TG-1 Selecting a Turf; TG-8 Turfgrass Improvement; TG-12 Turfgrass Cultivar Recommendations and TG-13 Turfgrass Maintenance Calendar. Or checkout the website http://www.urbanext.uiuc.edu/lawntalk/index.html

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