Crabgrass Prevention

Home Grown  by Keith Reed
Even though it’s cold and gloomy right now, we will all have a dose of spring fever very soon. With warmer weather will come an avalanche of promotional and advertising materials offering dozens and dozens of different combinations of fertilizer and weed control products. At the top of that list are products offering crabgrass control. The choices can be overwhelming. This information should help you increase your chances for successful weed control this season.

We talk a lot about timing when it comes to crabgrass. That is because the key to good control is having a preemergent herbicide in place (and activated) before the weed tries to germinate. Activated means having the product watered in properly. When you read the label, you will see that it states clearly how soon after application the product must be watered in (this applies for liquid applications as well as granular products). Even if you have your lawn treated by professionals, I suggest you ask how long you have to water it in as the time can vary depending on which product is used. If you are using a granular, don’t be too concerned if they don’t fully dissolve. The actual granules are often just corncob or other inert material used as a carrier for the herbicide.

Back to the timing issue, two factors are key. The first is the soil temperature as crabgrass germinates when the soil reaches 55 degrees. The second is the last freeze. A freeze is the best crabgrass control going as it will readily kill all crabgrass. Mother nature has a couple of very visible bio indicators to help us with soil temperature. As the common spring flowering plants forsythia and redbud begin to pass their peak flowering period, you can be assured the crabgrass will be coming on soon. To ballpark a calendar date, I would suggest having the materials in place by March the 15th.

Please remember, if you are late with your herbicide application, applying “a little extra” is not going to help. If this is the case, your best control option is to use a product containing the active ingredient dithiopyr to control those small early emerging weeds. And as always, PLEASE make sure you read the label and follow the directions carefully when using these products.

For more information on this or any other horticultural topic, you can contact Keith Reed, the Horticulturist in the Payne County Extension office. Keith can be reached via email at
keith.reed@okstate.edu, phone at 405-747-8320, or in person at the Payne County Extension office, located at 315 W. 6th in Stillwater.

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