Fall is the perfect time to get lawns ready for a strong spring, whether you’re overseeding, fertilizing or applying post-emergent herbicides. Peter Landschoot, professor of turfgrass science at Penn State College of Agricultural Science, says fall is also the time to get rid of hard to control weeds.
If you put down one application at the right time of year in the fall with a post emergence product, you’re going to pick up both the winter annuals and the perennials and the biennials for that matter. It’s a really great time to apply a broadleaf herbicide.
“If you put down one application at the right time of year in the fall with a post emergence product, you’re going to pick up both the winter annuals and the perennials and the biennials for that matter,” he says. “It’s a really great time to apply a broadleaf herbicide.”
“My experience is that most of the time, winter annuals can come in when there’s voids in the turf or, more commonly, when you’re doing establishment,” he says, noting that those aren’t the biggest problem in his area and the mid-Atlantic. “It’s the really tough to control weeds like wild violet and ground ivy. That’s really the best time to control those kinds of weeds and you can pick up the winter annuals when you’re doing that.”
As weeds are getting ready for winter, they’re drawing some of the sugars they produce down into their crowns to produce carbohydrates they will then use for food in the spring and summer. That means herbicides are being absorbed deep into the root systems as well.
Landschoot recommends applying a post-emergent herbicide right after the first frost before the foliage dies back. While the weeds might be out of sight, they shouldn’t be out of mind.
This time of year is also perfect for herbicide applications since there’s much less chance of turf damage. “Usually, this time of year, it’s going to be very, very safe but it’s going to be very slow before the plant picks it up,” Landschoot says, so be sure to wait a few days before mowing treated turf. And make sure that you don’t apply an herbicide too soon after mowing since you want to have plenty of foliage to intercept the herbicide.
But since fall is also the season for overseeding, Landschoot cautions against applying a post-emergent around new seedlings. He recommends mowing lawns a few times first and reading the label on your herbicide.
“There’s usually plenty of time to control them before they really cause a lot of problems in the stand at this time of the year because some of these winter annuals. They aren’t growing very fast and you can wait for a few weeks before you actually get on those and control them,” he says.
And if you’re putting down seed late in the year, Landschoot recommends forgoing a fall herbicide application.