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how to prevent weeds from growing around trees

Controlling weeds is a fight you can’t win entirely because they always grow back. But you can keep weeds under control by depriving new ones of the conditions they need to take root in the first place. Let’s look at how to prevent weeds from growing.

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Denman & Co.
401 W. Chapman Ave.
Orange, CA 92866
Ball weeder

Where to Find It

Yes, you can. Synthetic landscape fabrics provide a physical barrier to weeds yet allow air, water and nutrients through to plant roots. Spread the fabric over bare soil around trees and shrubs; overlap several inches of fabric at the seams. Anchor the material with U-shaped metal pins, then conceal it with 1 to 2 in. of mulch, such as stone or bark chips.

How to prevent weeds from growing around trees

Many gardeners dislike weeds growing around their pine trees. They make a yard look less cared for, and they can spread from the area beneath a pine tree to a nearby vegetable garden or landscape. Weeds also compete with trees for water and soil nutrients and can reduce the health and size of trees or other plants that they grow near. A combination of weeding and mulching is usually the best way to keep weeds from growing under pine trees. Herbicides are not recommended because some can harm pine trees can can be difficult to apply.


Plan on applying at least 3 inches of mulch to sufficiently prevent weeds. Apply the layer all around the base of the pine tree, but make sure to keep the mulch at least 6 to 12 inches away from the tree trunk. Mulches hold lots of moisture, and trees tend to have problems with diseases and insects when their trunks are consistently wet. Do not apply organic mulch over fabric mulch, because these mulches layered over each other can cause weeds to germinate.

Types of Mulch

After removing weeds through cultivation, applying a layer of mulch works well to prevent more weeds from growing in the future. Mulch has an initial cost and takes some work to spread, but it does not require very much maintenance. Mulch also provides extra nutrients to the trees and helps the soil retain moisture.

Mature trees have thick bark that protects them from many postemergent foliar herbicides, but pick the herbicide carefully to ensure it won’t soak into the tree’s roots. Those containing glyphosate, for example, typically are safe to spray around mature trees. The chemical doesn’t leach through the soil, so it shouldn’t reach the tree’s roots. Sethoxydim, another herbicide active ingredient, also is deemed safe to spray under trees to eliminate grass and weeds.

Even safe herbicides can hurt your tree if not applied carefully. The spray saves you time and labor when you want to rid the drip line of weeds and grass, but without the proper precautions, you can inadvertently harm your tree. Cover the trunk base with plastic or cardboard to prevent herbicide drift, which is where droplets blow in the wind to hit unwanted areas. Bark typically protects a mature tree, but green and thin barks are vulnerable. In addition, sprays can sneak into small chinks in the bark, such as cuts from a weed trimmer. Covering suckers, or immature trees that shoot up from the trunk base, prevents the young bark from absorbing the chemical into the main tree’s system. Removing suckers as soon as they appear eliminates this concern. Choose a day with no wind so that droplets don’t float over to the tree’s leaves; a few drops won’t harm the tree, but a significant amount can stress or kill it.

Pick the Right One

Many pre-emergent herbicides, or those that keep weed and grass seeds from germinating, are granules you spread and mix into the soil around your tree. These work only before seedlings appear, and they aren’t effective against grass that creeps in using rhizomes. Postemergent herbicides, however, often appear in spray form, allowing you to dose large areas under the tree or pick a single plant to target with the liquid. Many of these travel into the plants through the leaves or blades, killing them from within. Read the label carefully and apply only at the recommended rates; some herbicides can affect woody plants if applied at high rates.

Instead of constantly monitoring the area under the tree with herbicide spray in hand, take steps to prevent weeds and grass from getting a foothold. Mulch under the tree to help prevent seeds from germinating. A 4-inch layer of mulch won’t completely prevent weeds from germinating, but they will be easier to pull before they become established. For extra protection, place landscape fabric under the mulch. The landscape fabric prevents seeds and sunlight from reaching the soil. Unlike plastic, landscape fabric is a woven material that allows water pass through to the tree’s roots.

Keeping the Tree Safe

Grass and weeds under your favorite tree’s canopy can look overgrown and messy, but more important, they compete with the tree for moisture and nutrients. Finding the right herbicide to spray under your tree saves you the hassle of hand-pulling weeds and grass without harming the tree, but you must apply the herbicide properly to prevent accidental damage to the tree.