Do My Trees Have Herbicide Damage?

One of the many different symptoms of herbicide injury to a tree are curling or cupping leaves, but there are others.

Published March 1, 2010, By KEVIN BASSETT

The use of herbicides and other lawn care chemicals around trees can be very damaging. Before using any chemical in your landscape or near your trees, READ THE LABEL. Many herbicides are made specifically for turf, and are not designed or intended to be used near trees. There chemicals will have information on the label specifying the materials cannot be applied near trees.

There are a number of very important considerations that need addressing before applying herbicides. What is "close to a tree"? Considering tree root systems cover huge areas and volumes of soil, the use of some herbicides should not be allowed anywhere on the property. That statement sounds extreme, but arborists know that many textbooks depict tree root systems as ending at the limits of the canopy, or what is often referred to as the drip line. In practice, a tree's root system will grow in soils covering a much greater area than the drip line. Research shows that the total root area of a tree may be as much as four to seven times the area under the canopy.

Tree roots are opportunistic; they grow where they find what they need. They seek loose, well-aerated soil, and moisture.

Broadleaf herbicides are formulated to kill broadleaf weeds. Trees are broadleaf plants. So, using a herbicide may rid you of your dandelion problem, but it may also be picked up by the root system of the old Oak tree and cause serious problems.

Symptoms of herbicide include leaf curling or cupping, browning of the tissue between the leaf veins, leaf shedding, and branch and limb dieback. It is possible herbicides for use on turfgrass can kill your trees. So, be very careful when using these products and realize the turf and the tree roots may be sharing the same soil. As mentioned before, when using home and garden chemicals, always READ THE LABEL. If you have any questions concerning the product, get them answered by an expert or call the manufacturer before using the material. If you suspect that your trees may have been affected by an application of herbicide, call your certified arborist. In some cases, we can help the tree get past the initial injury.