What Kills Crabgrass? Two Methods that Worked for Us

by tracy on July 18, 2011

Green home certification points are provided for including a area-friendly landscape and water-efficient irrigation system in the construction or renovation of a green home.

Upgrading our current homes to include these features is one way all of us can make a difference. With this in mind, my husband and I had a new green irrigation system installed at our home earlier this year. The old one wasn’t worth saving.

The grass needed quite a bit of TLC due to both the construction of the new irrigation system and a particularly hard Florida winter. It took many hours to prepare and patch the dead portions of the lawn. What was the culprit behind the majority of those large damaged areas? CRABGRASS! It can’t survive the cold.

Most lawn services don’t address crabgrass leaving the war against this particularly invasive weed up to the homeowner. Not wanting to face the same problems with our yard next spring, we decided to try to keep large patches of this weed from forming this year. We tried a natural and a chemical option and found success with both. However, the chemical method traumatized the surrounding grass and, of course, is not environmentally preferable.

Here’s what we found to work:

* Apply a Crabgrass Pre-emergent in the Spring: Prevention is your first step. We live in Florida and according to the University of Florida, a pre-emergent should be applied around February 15th. One such product is Scotts Crabgrass Preventer. This helps but if your neighbors don’t do the same and/or you employ a lawn mowing service, crabgrass seeds will eventually germinate in your yard.

Don’t assume the pre-emergent applied by your lawn service includes crabgrass prevention. Because this component is pricey, it’s left out of the mix.

For those of you that don’t live in Florida, utilize the free information and advice from your local Extension Agency to find out what products and methods they recommend for your area. For a national list of Extension Agency offices, visit http://www.csrees.usda.gov/Extension/.

* Killing Crabgrass Naturally with Baking Soda: Mix ½ cup of baking soda and 1 teaspoon of cinnamon in a gallon of water and spray it on the crabgrass and surrounding area. You want to cover at least a foot all the way around the crabgrass infestation in order to address the runners.

The baking soda causes the crabgrass to burn in the sun turning it black, but the surrounding St. Augustine is not affected. Apply it early in the morning when the dew is still on the grass and let it bake in the sun. Pick a day when the sprinklers won’t be running and rain isn’t predicted until late in the day.

I would describe this method as hit or miss because some areas burned up within a day or two and others required additional applications. Not sure why.

Depending upon the size of your yard and crabgrass invasion, you may want to purchase the industrial size bag of baking soda at Costco.

* Celsius by Bayer: This chemical attacks over 120 different weeds without killing the following warm-season turfs: St. Augustine, Zoysia, Bermudagrass and Centipedegrass. This is pretty amazing stuff but it ain’t cheap. The 10oz bottle pictured here carried an $85.00 price tag, but…..only a small amount is required per gallon of water.

Our local “Do-It-Yourself” pest control retail stores carry this product but charge around $100.00 for it. Look for an agribusiness store in your area such as BWI. We’ve found their

Crabgrass sprayed with Celsius

prices to be more reasonable.

Talk to your lawn service before you spray Celsius. If they have recently applied a weed killer, your application of Celsius may compromise the surrounding turf. We found that out the hard way. It didn’t kill it, but it knocked it for a loop.

Read the directions! This stuff works but you have to play by their rules.

As with the baking soda method described above, apply Celsius on a day when the sprinklers won’t be running and rain isn’t predicted until at least late in the afternoon. Spray a foot in all directions beyond the crabgrass patch to eliminate the runners.

Be patient. It takes a couple weeks for the crabgrass to turn a purple color indicating it’s on its way out.

Also, I would suggest adding food coloring or Easter egg coloring tablets to the mix so you’ll know where you’ve sprayed. You don’t want to overdo it.

It has been our experience that eliminating this weed is not easy. Spraying once and calling it day for the season isn’t going to cut it no matter what product or method you select. You can certainly take a big chunk of the problem with your first application, but you’ll more than likely miss some areas and seeds will continue to germinate. It’s a season long battle.

If you’ve had success waging war against crabgrass, I’ll love to hear your story. Please add a comment below.

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