By Lisa Valle
University of Illinois Extension Ogle County, Extension Program Coordinator
Thanks to our early spring, many homeowners are finding that, despite having put down crabgrass preventer, they are seeing more crabgrass and other annual grass weeds than ever.
“Timing this year was very difficult,” said University of Illinois Extension Horticulture Educator Richard Hentschel. “If the preventer was put down at the normal time, there would have been annual grass weed seeds that would have been in a development stage at which they would not have been affected.”
Because annual grass weed seed can germinate all season long if the conditions are right, a second application of preventer later this year could prove useful. However, not all crabgrass preventers can be applied a second time, so be sure to check the label.
Perennial grassy weeds, which include tall fescue, nimblewill and quackgrass, are also causing problems in lawns. 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.
Unfortunately, Hentschel said, in many cases, the material will discolor the lawn, and more than one application may be needed.
Homeowners can remove the weeds manually, or use a non-selective weed control product. In either case, they will need to repair the lawn by filling in the holes left behind after digging the grass weeds out or patching with sod. 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 the 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, and may require a repeat application of a control product. Some of the better products contain three active ingredients — 2-4D, MCPP and Dicamba.
“There have, of course, been dandelions everywhere, and if they are not controlled this spring, waiting until fall is your next chance,” Hentschel said. “The bonus of controlling dandelions now 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.”
One of the best ways to control lawn weeds is to prevent them. Mow the lawn one notch higher for the rest of the summer. Higher turf means deeper roots, which keep the lawn healthier, thicker and more competitive with weeds.
“That taller lawn also shades the soil, preventing weed seeds from germinating, and retains more moisture, so the lawn stays greener longer into the summer,” Hentschel said. “If the lawn is always thin, consider overseeding every year to maintain a thicker, fuller lawn.”
When over-seeding is done using newer disease-resistant grasses, disease kills the older varieties, leaving the more robust variety in its place.
Because of the warm temperatures, lawns have been mowed many times already this year. Sharpening the mower blade at least once during the growing season is recommended. A mower performs better with a sharp blade and generates less pollution because the engine will not be working as hard. A mulching mower will not work properly if the blade is dull.
“If the edges of the cut grass look torn or shredded, it is time to sharpen the blade,” said Hentschel.
From the June 6-12, 2012, issue