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Destroy Weeds Without Killing the Lawn


Destroying weeds in your lawn without killing the grass is not easy, but it can be done.

While manufacturers advertise products that claim to kill weeds in your lawn, if you read the fine print, you’ll learn that most tell you not to get the spray on the grass. That means you need a very accurate sprayer or granular spread and absolutely no wind. As you know, if you use glyphosate, aka Roundup, virtually every piece of vegetation that the spray hits will die.

What’s interesting is that the reason we have no new state-of-the-art herbicides is we need new “safener” products. A safener is a chemical added to the herbicide chemicals to make the product safer for the plants you don’t want to kill. This is a bigger problem for crop farms, of course, but it also hits home for us, too.

Non-Chemical Choices

Before you resort to difficult broad-spectrum sprays, there are two tried-and-true methods of controlling weeds in your lawn.

The first, which seems counterintuitive, is to not mow your lawn too short. Keep your lawn at three inches or more in height to encourage the grass to grow thick. The thick grass will naturally help push back the weeds.

When you mow, only cut the grass back 30% at a time. So, if your lawn is about four inches tall, it’s time to mow it down to three inches. Taking more than 30% off stresses the grass (I know—it sounds like the grass needs Valium), but anxiety-ridden grass doesn’t grow thick and strong. And mow more often. The grass is happiest with frequent haircuts that keep it at three inches, but weeds prefer long hair.

The second method is labor intensive, and I’m not sure I like it. You pull out the unwanted plants, roots, and all (roots are very important to get), by hand. This is best done when the ground is really wet. Be sure to fill in any holes left by the unwanted plants to keep your yard nice and flat.

Spray Choices

There’s a recipe for weed control consisting of vinegar, salt, and dishwashing soap. I tried it. I noticed I had to use quite a bit of it, but the weeds did turn brown and withered. I was so happy—until after the next rain when they reappeared with a vengeance. Apparently, you need gallons of the stuff to get it to soak down to the roots. And, of course, you shouldn’t get it on the vegetation you want to keep, but that’s pretty easy with a little hand sprayer. The Penn State Extension recommends several postemergence chemical products (those are products you put on the weeds you see, the ones that already emerged from the ground). Mesotrione, sold as the brand name Tenacity, seems to be a strong choice. These products help control several different unwanted grasses and plants (aka weeds), including crabgrass, yellow foxtail, and some broadleaf invaders. Once applied, you may get a whitish look to your lawn as the plants die, and you may need to apply it more than once to gain control. They also suggest Topramezone, brand name Pylex, which they say is like Tenacity.

Timing Is Everything, Apparently

The time of year you apply the chemical may help, according to North Dakota State University. If you spray the weed killer of your choice in the fall—when the days are shorter and the nights are colder—the plants will suck the stuff up and send it down into the root system. The plants are trying to fill the roots with nutrients to protect themselves for the upcoming winter, but you’re giving them stuff that infects the entire root system, so they die and don’t reappear in the spring.

The way this works did help me understand why my brother, a landscaping pro, insisted that I use the weed whacker to cut back all the weeds before I applied Roundup. I just wanted to kill the weeds and skip the labor-intensive weed whacking around my fences, but I did as I was advised, and sure enough, I only have one more trip with the sprayer to knock the weeds back again. That’s only two sprays for the season, and I want to time the second one in the fall, so the weeds enjoy a permanent nap. (The article from North Dakota State with this tip includes many other good ideas for weed control, so go read it. But remember, you learned about that article here.)

And, if you’re friends with a golf course maintenance expert, talk with him or her. Find out what products golf courses in your area use to keep weeds out of the turf, as these products are at least somewhat safe for human exposure, likely do not harm the precious golf course turf, and are targeting local species of invading plants.

But be smart: Buying directly from a golf outlet might be pricey. Instead, hire your local landscaping/mowing company which might have some of the products on hand and be willing to apply it. When dealing with any type of chemicals, leaving it to the professionals—who are trained to avoid exposure and misuse of the product—is truly money well spent.

Posted on July 20, 2023

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