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Pre-Emergent & Post-Emergent Herbicides

By Debbie Roland, Master Gardener

Timing is everything when you apply a pre-emergent, a control for warm-season annual weeds. They work by preventing weed seeds from germinating and should be applied in early spring (January-March) before the soil temperature has warmed to 55 degrees. For weeds that sprout throughout the summer, a second application may be required in June or July. To control cool-season annual weeds, apply a pre-emergent herbicide in early fall (August to September). It must be distributed evenly and if you miss areas, they will be very visible during the growing season.

It is hard to set an exact date for application because of the variations of soil temperature from year to year. To find the best time to apply pre-emergents in your yard, note when the weeds begin to sprout this year and count back two or three weeks. Apply yours at that time next year. If you wait until after the weeds emerge, the herbicide won't have any effect.

If your weeds are already growing, you can apply a post-emergent. Post-emergents work by destroying already established weeds. Beware, however, some target specific weeds, while others destroy everything green, whether they're weeds, your grass, flowers or shrubs. Always, always read the application instructions on the label and follow them precisely.

These products require a minimal amount of labor and hopefully each season will lessen the need for their use. Since we live in West Texas where the wind is always blowing seeds from your neighbor’s yard, the kids are running through with seeds on their shoes and the birds are making their deposits, you will likely never be completely weed free.

Remember to be good stewards of your yard and use all chemicals wisely to be sure you, your neighbors and our water sources are safe. For more information, go to

SAVE THE DATE: It’s back. The Permian Basin Master Gardener Plant Sale will be held April 13 in Bldg. A at the Ector County Coliseum. Mark your calendar and see you there!

Please contact the AgriLife office in Odessa at 498-4071 or in Midland at 686-4700 for more gardening information.


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