Spring Is Almost Here…Time to Think About Weeds in Lawns

— Written By Bill Hanlin and last updated by JoAnne Gryder

The warm weather we had this past weekend has many gardeners hoping for an early weedkillerspring. I have gotten calls over the past few weeks from people who want to apply something that will prevent weeds from coming up in their lawns. These weed killers are called pre-emergent herbicides, and they must be applied at a certain time in order to get the control you want.

Pre-emergent herbicides do not prevent weed seeds from germinating. They work by killing the young seedling before it has a chance to break through the surface of the soil. If applied at the recommended rate, pre-emergent weed killers will not affect plants with an established root system.

Pre-emergent weed killer applied too early in the year will, likely, leach below the area where weed seeds are germinating. In this case, the gardener has just wasted their money since very little weed control will be achieved. Applying the weed killer too late will also be ineffective because the newly germinated weeds will have time to establish a root system.

So how do you know when to apply a pre-emergent weed killer? The label on the container will give you a general idea of when to apply. These recommendations are for different areas of the country and may not be accurate for our region. Using soil temperature recommendations, also on the container, gives you a more accurate time to apply since weed seeds germinate at fairly specific soil temperatures.

Finally, do not confuse pre-emergent herbicides with post-emergent weed killers. Post-emergent herbicides kill weeds after the weeds have come up and usually have no affect on weeds that have not germinated. Read the label closely to find out which type of herbicide you want to purchase and the times when they can be applied for maximum effectiveness.