Late Summer And Fall Are Times To Control Broadleaf Weeds

If your lush green lawn comprises more weeds than grass, there's no time like the present to treat your turfgrass for broadleaf weeds, says a turfgrass expert in Penn State's College of Agricultural Sciences.

"The best way to control weeds is to keep your lawn adequately fertilized," says Peter Landschoot, associate professor of turfgrass science. "Never let weeds get a foothold in your lawn. You can prevent that by maintaining a dense turf."

Landschoot explains that broadleaf weeds include such plants as dandelions, clover, knotweed and ground ivy. "Weed grasses, like crabgrass, will die soon after the first frost, so there is little point in trying to control those weeds in the late summer or early fall," he says. "Crabgrass and other weeds can be controlled by using a pre-emergence herbicide in the spring."

Landschoot says homeowners can treat weeds using one or a combination of three methods:

Weed-and-Feed. Any product that contains granules of herbicide mixed with fertilizer is the most efficient means of weed control. "The herbicide eliminates the broadleaf weeds, and the fertilizer helps the turf to grow more dense," Landschoot says. He recommends waiting for a dew-laden morning to apply a granular product, because moisture must be present on the plants to make the granule stick to the leaves. "Make sure it says the product is for broadleaf weed control," he says. "If it says crabgrass control on the bag, do not use it."

Liquid application. In small areas, a 1.5- or 3-gallon hand sprayer is very effective for treating weeds. However, if not applied carefully, the herbicide will damage trees, shrubs, garden plants, perennials and other plants.

"You have to know what you are doing with liquid application," Landschoot says. "If you use too much, it will kill your lawn."

Pulling weeds manually. "Pulling weeds is intensive labor unless there are just a few weeds," Landschoot points out. "Many times it is ineffective because pulling weeds often leaves the tap root in the ground, allowing the weed to grow again."

Once a liquid herbicide is used in small areas, or weeds are pulled, a fertilizer can be applied to help the lawn fill in. If large areas have been treated with an herbicide, there is a waiting period of at least four weeks before the lawn can be reseeded.

"If you think you need to apply liquid herbicide and then reseed, make sure you leave enough time to get the turf established," Landschoot says. "For instance, if you apply herbicide on Labor Day, you won't reseed until October, which is usually too late."

Landschoot warns that herbicides can have environmental consequences if over used (applying more than the recommended amounts) or applied incorrectly.

"Always follow the directions on the label," he emphasizes. "Read them twice to make sure you understand them. If you're in doubt, ask the garden center manager or call the manufacturer if the product package lists a customer service phone number."

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