Lawn mower blight is a common issue that can seriously damage your trees and even kill them. Luckily, learning how to prevent lawn mower blight is simple: just keep mowers away from tree trunks, mulch around bases, trim overgrowth with hand shears, and create weed-free zones around trees.
The idea is to make sure the tree’s bark stays safe from mower blades or string trimmers.
7 Ways to Prevent Lawn Mower Blight
Eliminate Weeds from the Tree Base
Lawn mower blight happens when you repeatedly hit the trunk of a tree with a mower or string strimmer, causing severe injuries to the bark and leaving the tree exposed to diseases and pests. (You can learn more about these risks in our article, “What is Lawn Mower Blight?”). To prevent this damage, the first step is to remove any grass and weeds that are growing too close to the trunk.
Marianne C. Ophardt, a horticulture specialist at Washington State University, recommends starting by creating a 12-inch “weed-free zone” around the base of your trees. Here’s how to do it:
- Identify your weeds: A control method that works for one weed might not be as effective for another. Check out our article on common lawn weeds, or visit your local gardening center for expert advice.
- Apply the best control method: Simply pulling them out by hand isn’t always the best idea. For example, if you’re dealing with dandelions, applying a post-emergent herbicide containing 2,4-D will be more effective. In contrast, if you have chickweed, regular weeding might work just fine.
- Regularly monitor the area: Some weeds, like crabgrass, are highly invasive and can regrow from even the smallest root fragments. To avoid this, check the area regularly and eliminate young weeds as soon as you spot them.
Pro tip: Be careful when using systemic post-emergent herbicides like Roundup, especially around young trees. If the spray gets on the bark, the tree will soak it up, which can stunt its growth or make the leaves curl up. Always use a spray shield or precision nozzle to target just the weeds.
You can also try natural, safer alternatives like vinegar or boiling water. Learn more about all the options you have in our articles “Types of Post-Emergent Herbicides” and “Guide to Organic Herbicides.”
Also read:
- “Guide to Weed Control in Your Yard”
- “How to Get Rid of Crabgrass”
- “How to Get Rid of Dandelions”
- “How to Get Rid of Clover”
- “How to Get Rid of Nutsedge”
Install Edging
Once you’ve removed all the weeds surrounding your tree’s base, you need to edge the area to clearly define the boundary and make it harder for mower blades to accidentally hit the trunk. Plus, edging helps keep grass and weeds from creeping back in.
Experts often suggest using materials like bricks, concrete, vinyl, or cedar board for edging. These options are durable and create a solid barrier that lasts longer than metal or plastic, which can bend or break over time.
If you’re comfortable with DIY projects and have the right tools, see our guide “Garden Edging 101: Ideas and Tips for DIY Installation.” If not, it’s best to hire a professional. When you edge around a tree, you’ll need to dig up the soil first. But if you’re not careful, you’ll damage the tree’s roots. A pro knows how to do this safely and effectively. Professional edging services usually cost between $630 and $1,710, depending on the material you choose. You can find more info in our cost guide on landscape edging.
Add a Layer of Mulch
The next step is to add some mulch to the weed-free area. Mulch is basically a protective layer of material that you put on top of the soil. You can use wood chips, compost, straw, or shredded bark — there are other types of mulch, but these break down over time, enriching the soil while providing great weed suppression.
Richard Jauron, a horticulture expert from Iowa State University, recommends adding between 2 and 4 inches of mulch. That’s enough to create a buffer between your mower and the tree trunk to prevent any accidental damage. Find more information in our guide, “How to Mulch Around Trees.”
Pro tip: Avoid piling mulch up against the tree, or you’ll end up with a mulch volcano. This will only cause moisture buildup and attract pests. Instead, keep the mulch about 3 to 6 inches away from the trunk and taper it down as you get closer to the trunk.
Mow Carefully
If creating a clear area around your trees sounds like too much hassle, you can also prevent lawn mower blight by simply mowing carefully. Just make sure to stay about 3 to 4 inches away from the trunk — especially if the grass is growing right up against the tree.
Also, try to use a mower with a smaller deck or a push mower. This gives you better control and allows you to easily maneuver around the tree without getting too close and damaging the bark.
Also read:
Trim Grass with Hand Shears
While you might want to grab a string trimmer to tackle that tall, overgrown grass around your tree, experts like Jauron and Ophardt advise against it. String trimmers work well for cutting grass around signs, poles, and buildings, but when it comes to trees and large shrubs, the nylon line can easily nick the bark.
Instead, use hand shears to trim the grass that’s near your tree’s base. If you don’t have a reliable pair, check out our “Best Garden Shears” review to find one that fits your needs and budget.
Cage Your Trees
Another option is to build a protective cage around your trees. It isn’t the most aesthetic solution, but it’s a great way to shield your tree trunks and avoid lawn mower blight. It works particularly well if you have a standalone tree in your yard that you want to showcase, or if you have a lot of trees clustered together in one area.
Here’s how to do it:
- Get your materials: Use a sturdy wire mesh or heavy-duty plastic fencing that’s at least 12 inches tall.
- Clear the area around the trunk base: You’ll need at least a 3-inch space free of grass and weeds to prevent any growth that could sneak into the cage and cause problems.
- Secure the cage: Install the fencing or netting in the ground and use stakes if you need to keep it steady. Make sure it doesn’t touch the tree trunk — that’ll trap moisture against the bark.
Use a Tree Wrap
Tree wraps can also protect your trees from lawn mower blight, especially if they’re young or thin-barked trees. These products create a physical barrier between the trunk and potential sources of damage. However, you’ll have to remove them during the growing season to allow the tree to breathe.
Find more information on this in our article, “Tree Wrap: What It is, Why to Use It, and How”
FAQ About How to Prevent Lawn Mower Blight
What is the best time of the year to install protective barriers around trees?
The best time to install protective barriers like cages or wraps is in early spring, just before the growing season kicks off. This way, you can set them up while the trees are still dormant, which means they won’t be disturbed as they start to grow.
Can lawn mower blight be fixed?
If less than 25% of the bark around the tree trunk is damaged, your tree will likely bounce back. It’ll just need some extra care and attention. Make sure to give it the right amount of water, apply a balanced fertilizer, and prune any damaged or dead branches. (See our guide on “How to Save a Dying Tree” for more tips)
However, if the injury goes all the way around the trunk, the tree might not survive. In cases like this, it’s a good idea to talk to a lawn care or tree expert. They can help you figure out if there’s a way to save the tree. If the damage is too serious, they might recommend removing it to keep your yard safe. Curious about how much that could cost? Read our cost guide on tree removal.
What are the signs of lawn mower blight?
Signs of lawn mower blight include visible scrapes or cuts on the bark, exposed wood, and discoloration around the trunk. You may also notice signs of stress in the tree, such as wilting leaves or stunted growth.
When to Hire a Pro
If you want to effectively protect your trees from lawn mower blight, the best thing you can do is hire an expert. DIY solutions can be tempting, but they come with the risk of overlooking important details that could cause more harm. A professional knows how to assess your trees and implement the right protective measures, saving you the headache of trial and error.
Need help with lawn care, contact a lawn care pro in your area to keep your yard looking great.
Main Photo Credit: SKT Studio / Adobe Stock Free / License
