What a Year it has been for Crabgrass

Home Grown  by Keith Reed
The office has been swamped with calls about crabgrass this year. It seems like the plant is growing everywhere. Given the level of frustration from so many people, I thought a brief discussion on this weed might be helpful.

First of all, now is NOT the time to attempt to control this weed. It’s mature, tough and at the end of its life cycle. As a summer annual weed, it is almost done for the year and will die completely with our first frost. Attempts to control it chemically in turf areas will be marginal at best and harmful to your desirable turf at worst.

Crabgrass is most effectively controlled by applied a preemergent herbicide in the spring before the weed germinates. As far as timing, you can find information claiming any date from late February to April 1st as the key date by which the product must be applied and activated by rainfall or irrigation. The date isn’t as important as the soil temperature and our last freeze.

Crabgrass germinates when the soil warms to about 55 degrees. Fortunately, we don’t have to measure the temps daily to know time is approaching; we can just watch two very common plants for clues. When the redbuds and forsythias are at their peak, we know crabgrass germination will be happening very soon. In case you don’t know these plants, the redbud is the very common pinkish/purple flowered tree that dots our Payne County landscape. The forsythia is the dominant yellow flowering shrub of the early spring.

This year turned out to be a perfect storm for crabgrass germination. We had an excess of moisture early in the year, giving the seeds plenty of opportunities to germinate. Couple this with lots of cool cloudy days that caused a delay in turfgrass growth and the race was on. The message here is don’t be too hard on yourself, or your landscape professional, if you applied pre-emergence products and had crabgrass anyway. The weed pressure was simply very, very high under these conditions.

It was this high pressure that was partially responsible for the crabgrass in areas that had been treated with preemergent. Most products suggest a second, or even third, follow-up for season long control. We can often skip the last application because of our hot, dry summers. That proved not to be the case this year.

The take-home for today is to mark your calendar now for next February. That will give you plenty of time to do your research, decide which products you would like to use (we can help you with that at the Payne County Extension Office) and find a day that is suitable to make the application.

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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