University of Connecticut

Crabgrass Control

Steve Rackliffe, Extension Instructor

Department of Plant Science

Crabgrass is a yearly problem in Connecticut lawns.  When determining control options, remember that the best control is a healthy, thick lawn.  This will smother out any weeds.  If the lawn is not growing properly, get a soil test and correct any fertility problems.

When crabgrass is only a minor problem in an otherwise healthy lawn the best control method is pre-emergent herbicides applied in the spring.  Many spring fertilizers are sold with crabgrass preventer.  Timing is critical for this to work because the herbicide will not be effective after the crabgrass is out of the ground and actively growing.  Typically, it is recommended to apply this material when the forsythia is in full bloom.

In order to correct or re-establish turf grass varieties, you have a few options. If crabgrass infestations were not serious, the recommendation would be to wait until next spring and assess the amount of desirable grasses still in your lawn. Spring fertilization along with a pre-emergent product may be all that your lawn needs. For areas that were extremely thinned out, I would recommend trying option one, below. Options two and three are presented to homeowners who want to completely renovate their lawns.

Option one: Wait until the spring. Crabgrass will die with the first major frost. At the time of crabgrass death, it is usually too late to seed new plantings because the soil is too cold. Young plants that may germinate will be susceptible to death from winterkill. Here’s what to do:

1) Collect clippings this fall to catch and remove seed heads of existing crabgrass. This will help reduce the amount crabgrass next year.

2) In spring, rake off or de-thatch areas of dead crabgrass.

3) Seed with desired turf grass variety.

4) Apply Tupersan® (Siduron) for pre-emergent crabgrass control. Application of this product can be made at the time of seeding. To ensure control, a second 1/2 rate application of this product may be needed six weeks later.

Option two: Take aggressive action this fall with complete renovation. Fall is a good time to seed as competition from weeds is reduced and soil temperatures are warm and favor germination.

Here’s what to do:

1) Apply Round-Up® to entire crabgrass infested area. (Round- Up® will kill all desirable species as well as the crabgrass). Wait seven to 10 days.

2) Scalp existing dead crabgrass/turf grass. 

3) Rent a de-thatcher and if possible an aerifier.

4) Aggressively aerate and de-thatch in multiple directions.

5) Remove debris.

6) Overseed with desirable species.

7) Post care – proper water and fertilization.

8) Apply a pre-emergent herbicide in the spring.

Option Three: Take aggressive action this fall, partial renovation.

In this option, skip the Round-Up® Herbicide application and follow steps 2 through 8 from Option Two, above.

The information in this material is for education purposes.  The recommendations contained are based on available knowledge at the time of printing.  Any reference to a commercial product, trade name or brand name is for information only and no endorsement or approval is intended.  The Cooperative Extension System does not guarantee or warrant the standard of any product referenced or imply approval of the product to the exclusion of others which might also be available.

All agrochemicals/pesticides listed are registered for suggested uses in accordance with federal and Connecticut state laws and regulations as of the date of printing.  If the information does not agree with the current labeling, follow the label instructions.  The label is the law.

Warning: Agrichemical/Pesticides are dangerous.  Read and follow all instructions and safety precautions on labels.  Carefully handle and store agrichemicals/pesticides in original labeled containers out of the reach of children, pets or livestock.  Dispose of empty containers immediately in a safe manner and place.  Contact the Connecticut Department of Environmental Protection for current regulations. 

The user of this information assumes all risks for personal injury or property damage.                         

Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914 in cooperation with the U.S. Department of Agriculture, Kirklyn M. Kerr, Director, Cooperative Extension System, University of Connecticut, Storrs.  The Connecticut Cooperative Extension System is an equal opportunity employer.