Although it’s only mid-August, you may have noticed that some maples and other deciduous trees are turning the color expected in fall. This is a sign of stress, although with some older trees it looks like this happens every year.

Last season, drought was the biggest stress problem for trees. This year we had adequate or above-average rainfall. Are trees still suffering from drought?

The difficulty of correcting tree problems is compounded by the delayed effects of stress and root damage. What you are seeing now may have started months or even years ago, since above-ground symptoms are usually delayed when problems occur below ground.

When roots die, there is less support for the canopy above, resulting in subsequent discoloration or death. Structural damage is the classic example of this; a tree may look fine immediately after the initial injury, but three to five years later it looks terrible.

Another factor to consider is that although the trees here appear green in the third week of August, they have already passed their active growth phase for 2024 and are already preparing for winter dormancy. This process is dictated by the length of daylight, so whether you like it or not, the days are getting noticeably shorter. As the process continues, the green chlorophyll in the leaves dissolves and other pigment colors such as yellow and orange become visible.

Some trees wilt early. Drought can play a role, but chronically problematic trees have problems with the root or trunk system that reduce the flow of water and nutrients to the leaves. Trees next to roads, driveways or buildings often show early fall color due to soil and site problems. These include excessive heat from road surfaces, compacted and/or unsuitable soil and road salts accumulating in the soil.

Carefully examine the trunks of trees that are turning color early. Look for wounds or injuries, including scarred or calloused areas from past damage. Visible wood rot fungi growing from the trunk also indicate some type of past injury. These trees have a reduced capacity to absorb water and nutrients and therefore may begin to go dormant early.

There is not much that can be done for mature shade trees that show early color. Dry soil can be watered if necessary, although this will not cause the trees to turn green immediately. Avoiding additional stress is beneficial for the future. Wounds on trunks are best left alone, but dead wood should be removed. Any large tree suspected of having structural problems should be examined by a trained arborist.

Bruce Spangenberg is a horticulture instructor at the University of Wisconsin Extension’s Iron County Extension. Email him yard and garden questions at [email protected] or call him at 715-561-2695.