Getting intimate with lawn weeds

February 13, 2013 

When we consider all types of ornamental plants, Clint Waltz, extension turf specialist, says people are most intimate with grasses. What does he mean by that? People look at flowers, sit under shade trees and prune shrubs, but we actually walk, play and live on lawn grasses. Turf creates a place for us to walk, run, play, exercise, sit and grill, etc. We love to live close to our lawn grasses.

During the winter, most of us have spent little time being intimate with our lawns. We have been inside dodging the cold. As we head back outside as temperatures climb, we notice that our lawns do not look their best. Should we be concerned?

I encourage people not to look too closely at their lawns right now. Lawns are in the “ugly duckling” stage now. Lawns are prematurely greening up now and are in the ugly, half-green stage. Weeds left over from the fall and winter are beginning to grow rapidly and bloom. Lawns may not be very pretty right now. Give them a couple of months, and they should look much better. However, there are some things we can do to help lawns deal with weeds.

The winter weeds we see now have little competition from the lawn and grow rapidly. These large weeds alarm homeowners. However, these weeds are often very difficult to kill at this time of year for several reasons. Once a weed gets large enough to bloom, the weed can be very difficult to kill. Also, using herbicides during lawn green-up can damage or kill your lawn. Since these winter weeds should disappear on their own as temperatures climb in April and May, you may want to let them stay until then.

If you want to reduce these weeds safely, consider some alternatives. Mow the lawn closely and collect the clippings. Collecting the clippings helps to remove seeds that will grow in following years. You can apply a herbicide (weed killer) that will kill some of the weeds. Be realistic and careful with herbicides at this time of year. First, no weed killer kills all weeds. Also, applying weed killers during lawn green-up can damage the lawn. If you use them, select weed killers carefully, apply them only to healthy lawns, avoid applications during green-up and read and follow all label directions when using any herbicide or pesticide.

Herbicides containing 2,4-D and dicamba (banvel) will kill many broadleaf weeds. Larger weeds may be hard to kill, so you may want to try two applications if one does not work. Do not over-apply these weed killers.

Controlling the weeds you see in lawns now may or may not work. However, if lawn weeds are a concern to you, prevent the weeds you are going to see this summer. Summer weeds such as crabgrass, lespedeza, goose grass and others begin to grow once soil temperatures get warm -- about 55 degrees or warmer 4 inches deep. Our current warm weather will probably mean these weeds will come up earlier than in the past. If you plan to prevent these summer weeds, apply these herbicides immediately.

Select pre-emergence herbicides based on the lawn type and weeds you have. Atrazine can be used on zoysia, centipede and St. Augustine lawns. It can also be used on Bermuda grass if it is fully dormant (brown). Atrazine prevents many broadleaf weeds and annual bluegrass. It will not control crabgrass or goose grass.

On all warm season grasses, you can use other pre-emergence herbicides besides Atrazine. These are better at preventing grasses (especially crabgrass), but will prevent some broadleaf weeds. These include Halts (pendamethalin), Balan (benefin), dithiopyr, and XL (benefin plus oryzalin). These weed killers should be applied before weeds emerge. If applied after weeds emerge, expect poor weed control. So we need to apply these as soon as possible.

Weed and feed fertilizers have a fertilizer and a herbicide in one product. Weed and feed fertilizers containing nitrogen should be avoided until April. It is best to apply preventive herbicides at this time of year by themselves or in fertilizer combinations containing no nitrogen. Read and follow all herbicide label directions.

Willie Chance works with the University of Georgia Center for Urban Agriculture and helps to train the turf and landscape industry.

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