Don’t give up. It is possible to win the battle against the weeds that seem bent on taking over every square inch of your lawn. But you can’t wish them away; if you want to combat lawn weeds effectively, you have to be as relentless as they are.
Although everyone would like a one-shot method–get rid of them today and never worry about them again–the effort to ward off lawn weeds lasts from spring all the way through fall. You can take winter off, because the weeds do.
In fact, each time you mow the lawn you either help your cause or hurt it, depending on how low you cut the grass.
Cropping the grass too short weakens it, robbing it of a chance to thrive and outcompete weeds. Repeated crewcuts for the lawn eventually cause the weakened grass to thin out, making room for opportunistic weeds to fill the space.
“Most people think they have to cut the grass really short, like an inch tall, because that’s how golf courses look,” says Richard Jacobi, president of the 48-year-old firm Greenlawn Landscaping, on Chicago’s Northwest Side. “But golf courses have a different kind of grass than most back yards do. The grass in your lawn can’t go that short.”
Jacobi and Bruce Branham, associate professor of turf management at the University of Illinois Urbana-Champaign, both advise maintaining a lawn height of about 2.5 inches. Setting your mower blades that high, Branham says, keeps grass blades long so they can feed the roots below sufficiently via photosynthesis, the biological process by which leaves digest carbon dioxide and water.
On top of that, he says, “when you raise the mowing height, these bigger, healthier blades of grass can shade out the weed seeds.” The seeds of most weeds only sprout if they get enough sunlight, he notes, and the few weedlings that do sprout under the shade of lawn grass may not be able to get enough sun that they can outgrow the lawn and start to bully it for water, sunlight and nutrients.
Letting the grass grow higher also gives the person who runs the mower a break. Because you should never cut off more than one-third of the grass’s height, you can go longer between mowings on a high-lawn program. A lawn that’s to be cut to an inch tall is ready for mowing when after half an inch of growth, while its counterpart that’s allowed to stay 2.5 inches can put on more than an inch of new growth before the next mowing.
Regular fertilization of the lawn also helps keep down weeds. “The lawns that are most prone to weed infestations are the short, yellow ones that get cut too short and don’t get fertilized,” Branham says.
His recommended fertilizer plan has feedings for the lawn in late May, early September and late October. The fall feedings are most important, because the lawn’s roots metabolize the nitrogen then so they are prepped for a head start the following spring.
Strengthening the lawn against weeds is only half the battle; the other half is eliminating the weeds themselves. That usually means deploying an herbicide. Although many people distrust chemical herbicides these days, Branham and others advise that if they are used strategically (which means, among other things, that if they are used as lightly and infrequently as possible), they do their job without causing undue problems.
In small areas with weeds, or if there are only a few weeds, consider hand-digging them. When the ground is moist, uproot the entire weed, roots and all. (When the soil is dry, the roots are more apt to break off and stay in the ground to resprout.)
Toward using as little herbicide as possible, be sure you know what kind of weeds you’re fighting. There are two general categories, each easily recognized by its name: broadleaf weeds and grassy weeds. A subset of the second set is known as sedges.
It’s not necessary to know whether your broadleaf weed is plantain or ground ivy, says Don Ferrari, golf course superintendent at Seven Bridges Golf Club in Woodridge. “Knowing the category is enough.”
Read the labels of herbicides available at your hardware store or garden center to determine which products work on your problem category.
Follow the instructions on the label carefully, and when possible apply the herbicide directly to the weeds rather than broadcast it over the whole lawn as a preventive measure.
Branham says that most homeowners should not consider herbicide application a yearly project. If it’s done right once and the lawn is treated well otherwise, he says, “the herbicide is for getting a clean slate, eliminating a big weed problem. Then you keep it from happening again with good (lawn) cultural practices.”
Jacobi says two cultural practices not to be skipped are the fall application of a “weed-and-feed” lawn fertilizer, a product formulated to both nourish the turf grass and discourage any weed seeds that have fallen into the lawn during the season; and a spring application of a pre-emergent weed-killer, either chemical or organic. The pre-emergents are especially useful on two pernicious annual weeds: dandelions and crabgrass.
There’s another practice Ferrari recommends: lowering your standards. Especially now that the rampant use of chemicals on lawn and garden are frowned upon, he says, “you have to raise your threshold for how many weeds is tolerable.”
He’s not advocating knuckling under to weeds–which could ultimately lead to forsaking the lawn entirely–but adopting a placid attitude.
“You’ll never get rid of all of the weeds anyway,” Ferrari says, “so let a few of them slide.”
