Early spring, before the warm season really starts, is a good time to do a special kind of herbicide application known as a pre-emergent herbicide. Pre-emergent herbicide applications help to eliminate weeds before they can grow. Some of the common summer grassy weeds that this treatment can prevent are crabgrass, foxtail, goosegrass, and sandbur.
Once the soil temperature rises it will be the perfect time to apply a weed preventer. The correct temperature means that it should be 55 or above for at least 2 days. Usually, this is at some point between March and April.
For most granules or liquids are the two main methods used to apply pre and post-emergent herbicides. It is vital that the active ingredient reaches into the soil, so if you are using granules you’ll need to water them in. If you’re using a liquid, it will seep in on its own.
It is important to make sure you’re applying pre-emergents before the growing season because once weeds—such as crabgrass, or broadleaf weeds like dandelions, clover, ragweed, and carpetweed—are visible it’s too late and you’ll have to use different treatments such as a post-emergent herbicide weed killer. When using a post-emergent weed killer be careful during application because lawns and decorative plants can be burned or killed by these chemicals.
Apply pre-emergent herbicides in both late summer to early fall as well as early spring because this is when most weeds bloom. These pesticides have an active ingredient which does not stop weed seeds from germinating, but instead keep them from sprouting. This means that the application is best done just when the seeds germinate. This usually happens twice a year. For the fall application wait until temperatures drop to the mid-70’s for three to five days in a row. For some weeds, such as annual bluegrass, multiple applications over consecutive years may be necessary to achieve the level of control you’re looking for.
Pre-emergent herbicide applications will not last through consecutive seasons so it is necessary to apply them each year, twice a year, to get the weed control you want for your lawn.