Unseasonably warm weather has Kansas City homeowners thinking about summer weeds in the lawns, so many may be questioning when pre-emergent herbicides should be applied.
The best way to control summer weeds is timely application of pre-emergent herbicides in early spring to kill the weed seed as they germinate. This is especially true of the grassy weeds, such as crabgrass, foxtail and goosegrass.
Annual grassy weeds are very similar to the lawn turf grasses that we are trying to grow, and there are few post emergent herbicides that will control crabgrass without injuring the good turf grass. So the best way to reduce the amount of weeds is to have a thick, healthy turf that reduces the amount of sunlight that reaches the soil surface.
The most common grassy weeds in Kansas City are large crabgrass, yellow foxtail, and goosegrass. Crabgrass and foxtail will grow in any soil type and under any condition. Goosegrass occurs in areas with heavy traffic.
Crabgrass, foxtail and goosegrass will start producing seeds in mid-summer and will produce seed until frost. These seeds will lay dormant until the soil temperature reaches 55 degrees, and then they will start to germinate.
Wait for the forsythia to bloom! Timing is everything when it comes to pre-emergent herbicide application. You need herbicide in the soil when the seeds are ready to germinate. In Kansas City, look for crabgrass germination to happen when night time temperatures are consistently above 55 degrees for several days in mid to late April.
If you are planning on reseeding your lawn, you should not use a PREVENT!® in early spring. Otherwise, PREVENT!® will kill the grass seeds as they germinate.