If you have a lawn and complain about weeds every summer — listen up. Now is the time of year that proactive gardeners put down “pre-emergent herbicide.”
Let’s start with the basics: what is a pre-emergent herbicide? This is a type of herbicide that controls plant growth as it’s germinating and prevents them from breaking through the soil surface, or emerging (acting before the plant comes up.) Once the plant has broken through the soil surface, this type of herbicide has zero control.
How exactly do they do this? These chemicals disrupt plant biological processes like cell division and reproduction to halt growth in the layer of soil that has been treated. Established plants that have root systems below this treated layer of soil can continue normal growth and development without being affected by the chemical. After a certain amount of time, the chemical breaks down and control of germinating plants stops.
Now that you know the basics, let’s dig into the details of how you can use a pre-emergent herbicide to prevent weeds. The first thing you’ll need to know is what plants you are trying to control. Take some time to visit aggieturf.tamu.edu and look through their gallery of common Texas lawn weeds. Look for a chemical based on the plants you’re trying to prevent. If you don’t remember, ask for an herbicide with broad spectrum control. If you call me or come into my office in the courthouse, we can talk through which one might work best for you.
The next thing to look at is your equipment. What do you have available to apply the herbicide? If you have a broadcast spreader, you can choose a chemical in a granular form. If not, you need some sort of spray equipment to apply the chemical. If you have neither, I suggest the broadcast spreader, even one of the small, handheld ones. For a larger lawn, you’ll want to invest in a push-type broadcast spreader. If you have a sprayer (either a backpack or handheld sprayer), make sure you’re uniformly applying the chemical. You’ll also want to calibrate the sprayer to know what rate of chemical you’re applying so you don’t over or under apply.
Another factor is the species of grass you’re trying to grow. Some chemicals will damage different turfgrasses, like atrazine or bermudagrass. Pay careful attention to the product’s label to make sure your desired species isn’t listed on the controlled species section. You’ll want to make the decision of which chemical to apply based on the three previous factors.
Once you’ve bought a chemical, you’ll need to read the label. The label will have instructions for application including the rate and method. Wear the proper protective equipment listed on the label as well.
If you’re spraying on your chemical, make sure your tank is mixed to the right concentration and know the amount of product you’re applying per square foot as you’re walking. If you’re applying a granule with a broadcast spreader, make sure you know the width your spreader will reach. Avoid overlapping so you aren’t wasting chemical. You might also consider splitting your application into two passes across your lawn, walking perpendicular on your second pass to ensure a more uniform application.
After that, many pre-emergent herbicides need a little water to move into the soil. If you water your lawn a quarter inch, that will help your chemical move into the top one inch of soil and start controlling germinating weeds. Different chemicals require different irrigation treatments, so check the label.
Now while your neighbors are fighting crabgrass, you can relax and enjoy your spring and summer free of annual weeds.
The AgriLife office is located at 100 W. Houston St., Sherman. For more information, visit www.Grayson.AgriLife.org.