Work now to control summer weeds

Many of us don’t think about weed control until our lawns suddenly seem to sprout weeds overnight. In reality, those robust weeds are thriving in dormant turf germinated last fall. The key is acting early. Don’t wait until summer to address warm-season weeds such as crabgrass and chamberbitter.

While a few herbicides are effective on weeds that have already emerged, the best control for most grassy and broadleaf annual weeds comes from applying a preemergence herbicide. These products must be applied prior to seed germination and weed emergence to be effective.

Because of the long growing season in Middle Georgia, University of Georgia turfgrass scientists recommend a split application of preemergence herbicides. Apply half of the recommended amount in early to mid-February, followed by the remaining half six to eight weeks later. If applying later in the season, apply as soon as possible and follow with the second application prior to green-up.

Grass type and proper weed identification are important before selecting a preemergence herbicide. Centipedegrass and St. Augustinegrass are among the more sensitive warm-season grasses, and using the wrong product may result in herbicide injury. Atrazine is commonly used on these turf types when applied according to label directions.

Herbicides should only be used on healthy, established lawns. Do not apply them to newly sprigged areas or lawns that will be reseeded in the near future. Other considerations, such as formulation type (granular versus liquid) and cost, depend on your available equipment and personal preference.

The lawn should receive at least a ½ inch of water within five days of application. This irrigation activates the herbicide and creates a chemical barrier in the top layer of soil, preventing newly germinated seedlings from becoming established.

Always follow label directions carefully. Certain herbicides can harm ornamentals and trees if applied too close to their root systems.

Product marketing often promotes combination “weed and feed” products that apply fertilizer and preemergence herbicide in one step. While this approach can be appropriate for cool-season grasses such as tall fescue, which grow in north Georgia but struggle in our summer heat, UGA turfgrass scientists discourage their use on warm-season turfgrasses grown in Middle Georgia. The reason is timing. Preemergence herbicides should be applied now, while fertilizer applications should wait until late April or early May, when warm-season grasses are actively growing.

For the robust weeds currently growing in your yard, hand-pulling or mowing is the safest approach. To reduce seed production that can contribute to next year’s weed problems, use a catcher on your lawn mower. Attempting to chemically control mature weeds may injure turfgrass as it begins to break dormancy.

For guidance on herbicide selection, contact your local county UGA Extension office or consult the turfgrass section of the Georgia Pest Management Handbook.

Kathy Hensley is the Agriculture and Natural Resources Program Assistant for University of Georgia’s Bibb County Extension. If you have other gardening or landscape questions, call Bibb County Extension at 478-310-5350 or email us at bibb.extension@uga.edu.