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Master Gardener: Prevent weeds now with a pre-emergent

Master Gardener: Prevent weeds now with a pre-emergent

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Apply a pre-emergent to stop weeds from growing in the future.

I had so much crab grass in my lawn this year. Is there anything I can do now to help with that problem for next year? MC

Weeds can be so frustrating, as they seem to be a constant battle. But there is something you can do right now to help for next year. You can apply a weed pre-emergent.

Two of the more popular pre-emergent products for grassy weeds are pendamethalin and prodiamine (scientific names — you’ll have to read the label on the pre-emergent product). For broadleaf weeds, you would need to apply a product containing isoxaben. For bermuda grass, you would apply these in late February to early March, late May to early June, and again in late August to mid-September. In other words: right now. For fescue, you would apply your pre-emergent in February to early March and late August to early September. Again: right now.

Typically, these products come in granular form, which need to be spread on your lawn at the recommended rate. After application, you will need to water them in as they dissolve to create a protective barrier on top of the soil. This chemical barrier is called a pre-emergent because it is a treatment you apply before the weeds emerge from the soil.

As they emerge, the chemical kills the weed, thereby minimizing your weed problem. However, one thing to remember is that this will likely be a multiseason process, as some weed seeds can remain dormant in the soil for several years. So if you just do one application, you will likely have marginal results.

One cautionary note: If you apply a pre-emergent, you cannot re-seed your fescue for two to six months. This is because the pre-emergent does not know the difference between a weed or fescue grass, and it will prevent your newly planted seed from becoming established.

Your primary defense again weeds (either grassy or broadleaf) is healthy, thick turf, as weeds tend to be opportunistic and love bare or thin spots in your grass. To help build healthy turf, you need to choose the correct variety for your conditions, water regularly when Mother Nature isn’t cooperating and feed (fertilize) your turf. This time of year, bermuda needs about 1 inch of water a week and fescue needs about 2 inches.

Fertilization needs to happen three to four times a year. The amount of fertilizer depends on the nutrients that are currently in your soil. To find out your nutrient levels, you will need to do a soil test. You can bring soil to the OSU Extension office in Tulsa, and we have complete instructions on how to collect your sample on our website. Just click on the “Hot Topics” button on our home page.

If you follow these instructions, you will likely just be a few seasons away from a healthy, beautiful lawn.


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You can get answers to all your gardening questions by calling the Tulsa Master Gardeners Help Line at 918-746-3701, dropping by our Diagnostic Center at 4116 E. 15th St., or by emailing us at mg@tulsamastergardeners.org.

You can get answers to all your gardening questions by calling the Tulsa Master Gardeners Help Line at 918-746-3701, dropping by our Diagnostic Center at 4116 E. 15th St., or by emailing us at mg@tulsamastergardeners.org.

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