The weeds in your lawn may look pretty when they bloom, but a healthy stand of any turfgrass doesn’t benefit from other plants growing in it, and the competition can cause it to lose vigor. Less healthy lawns are more suseptible to pests and diseases, so to control the weeds is really to promote overall good turf health.
Each lawngrass has its nemesis weeds. Some are grassy competitors and others broadleaf invaders; both usually spread by seed and underground runners. Your task: to stop first, their spread, and second, their cycle of reproduction. If one third of your lawn is covered by weeds in any season, it’s time to act.
When people attack the weeds they see, most use chemical controls called post-emergent herbicides. These ‘weed killers’ work on designated plants to dehydrate, rupture, or melt their tissues. They are formulated to control either broadleaf or grassy weeds in specific turfgrasses.
Spray the patch of weeds you see and at least a one foot margin around it. Never spray a dry lawn, and whenever possible, spray early on what promises to be a sunny day. A second application may be necessary, even to get a grip on common weeds. More exotic pests and those with enlarged roots like nutgrass and wild onion may take a specific chemical treatment to control.
Once you’ve lowered the weed count and slowed their spread, take out your calendar. Count back from the day you sprayed to just before the weeds would have sprouted, about eight to ten weeks. That’s the date to apply a different product next year, one that prevents weeds from sprouting. Most pre-emerge products are available as granules and are intended for broadcast across the entire lawn with a walk behind spreader.
After you have controlled the weeds, keeping ahead of them is as simple as fertilizing your lawn. Use combination products, the so-called ‘weed and feeds’ for lawns in good health, with less than ten percent weeds. The one-step does not “feed the weeds” as critics contend. Rather, the weed killer works first, and the fertilizer is then slowly released as the lawn recovers.
This is the unedited version of an article that appeared in Garden Almanac, a publication of GroGroup.