University of Illinois Extension

Summer Lawn Weeds

Given our early spring weather, many homeowners are finding out that even though a crabgrass preventer was put down, they are seeing more crabgrass and other annual grass weeds than they ever expected, said Richard Hentschel, a University of Illinois Extension horticulture educator.

"Timing this year was very difficult and even if put down about the normal time, there would have been annual grass weed seeds that would have been in a development stage and would not have been affected," said Hentschel. "Since annual grass weed seed can germinate all season long if the conditions are right, a later second application could prove useful this year."



Not all crabgrass preventers allow a second application, so be sure to read the labels carefully if this is a consideration. Our other grassy weeds are perennial and include tall fescue, nimblewill and quackgrass. The commercial lawn care companies may be able to treat the lawn with a product that will selectively remove one or more of these three weeds.

"In a lot of cases the material may discolor your lawn and more than one application is needed," he said. "Homeowners are left with manual removal or using a non-selective weed control product. In either case, repairing the lawn will be needed. Filling in the holes left behind by digging the grass weeds out and or preparing for patching with sod will need to be done. Make sure the lawn is level again so water will not stand in the repaired area."

Broad-leaved weeds have also enjoyed the early spring weather by getting off to a better than average start. Ground ivy, also called Creeping Charlie, has been aggressively leaving those shadier spots where it got started and running out into the full sun areas of the lawn.

As weeds go, Creeping Charlie is not easily managed. In many situations, a repeat application of a control product will be needed. Some of the better products contain three active ingredients, 2-4D, MCPP and Dicamba.

"There have, of course, been dandelions everywhere and if not controlled this spring, waiting till fall is your next chance," he said. "The bonus of controlling dandelions in the fall is that you get those plants that were already there in the spring as well as any that sprouted and grew in your lawn all summer too."

One of the best ways to control lawn weeds is to prevent them. It is a little late for New Year's resolutions, but resolve now to mow the lawn one notch higher for the rest of the summer. Higher turf means deeper roots and that makes for a healthier, thicker lawn which is more competitive with weeds.

"That taller lawn also shades the soil, preventing weed seeds from germinating and retains more moisture so the lawns stay greener longer into the summer," Hentschel said. "If the lawn is always thin, consider over-seeding every year to maintain a thicker, fuller lawn. When over-seeding is done using our newer disease-resistant grasses, the older varieties get replaced as they die due to disease, leaving a more robust variety in its place.

"The lawn has already been mowed many times already this year, and it is recommended to sharpen the mower blade at least once during the growing season. This is critical for a mulching mower to properly work and makes a regular mower perform better as well. A sharp blade also means less pollution as the engine will not be working as hard. If you need proof it is time to sharpen the blade, take a close look at the edges of the cut grass. It should not look torn or shredded."

Plant Roots