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Crabgrass Control Begins Now for Next Season

Crabgrass seeds turn reddish purple in late summer. (Ernie Reppe photo)

Crabgrass seeds turn reddish purple in late summer. (Ernie Reppe photo)

Questions about crabgrass control are coming to us in droves right now from at least two thirds of the United States and all of Canada. Ernie Reppe’s email from today is typical:

“I don’t know how things are out East for you, but people in the Midwest here are crazy about getting rid of crabgrass,” he wrote. ” I understand that crabgrass goes to seed about this time of year and that it dies with the first frost. Once the frost hits, is that when all the seeds fall off the plant? Or are they spreading during their entire growing season? I’ve attached a picture of some crabgrass from my back yard. Are those little purple things the seeds?”

Answering the last question first, the crabgrass seeds do turn purple in late summer and early autumn. They drop off after the first heavy frost kills the plants, which are annuals.

Eliminating those seeds is just one component of a crabgrass defense strategy. You can collect the seeds by digging the entire plant out of the ground, or snipping off the seeds with lawn scissors, or mowing low with a bagger attachment on the mower.

If you have a lawn heavily laden with crabgrass, a more aggressive strategy this fall can also help reduce the population next year. In that case, you’ll want to eliminate the seeds with one of the three strategies above — preferably pulling the entire plant — and then overseed with new grass seed.

If you do that, you may also want to consider dethatching and aerating just prior to overseeding. For an even more thorough approach, obtain a soil test first and apply any soil amendments such as limestone according to the recommendations on the test.

Dethatching will help scratch the surface of the soil and create good seed-to-soil contact. Aeration can reduce compaction and create a better soil environment for the new grass seedlings.

Now, here’s the really important part:

This fall be sure to clean leaves and other debris off your newly seeded lawn so that you’ll have as little reason as possible to rake next spring. Let the grass grow long (3-4 inches) in the spring because the tall grass plants will shade the surface of the soil — thereby blocking the sun from any crabgrass seeds that did fall to the ground from this fall, or any previous fall. Crabgrass seeds need light to germinate. Avoiding spring raking means you’re not stirring up those seeds in the soil, bringing them to the surface, and therefore increasing the likelihood of their germination.

Yes, you can apply corn gluten meal as a pre-emergent control in the spring at about the time of the forsythia bloom. But if you overseed this fall, you can let the new grass do the same job. It’s cheaper and, in the long run, easier.

About The Author

Paul Tukey

An international leader of the green movement, Mr. Tukey is a journalist, author, filmmaker, TV host, activist and award-winning public speaker, who is widely recognized as North America's leading advocate for landscape sustainability and toxic pesticide reduction strategies.

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  • Hank

    Paul I am in Gorham Maine and wish to know if it is too late to start a lawn. I have about 1000 sf of old lawn that actually looks quite bad so I wish to overseed it after applying about 1-2″ of quality loam/compost (at a mix of about 3:1). Thanks, Howard

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