With the calendar turning to September, the highly anticipated annual fall foliage color show across Wisconsin is on the horizon. However, every year we see scattered trees starting the show early. Several factors may be involved, but the early fall color has no relation to the exact arrival of fall or any forecast of how cold the upcoming winter will be.

Although leaves are still green, trees have advanced past their active growth period for 2025 and are preparing for winter dormancy. The length of daylight, more specifically increasing darkness over consecutive days and weeks, drives this process. Eventually green chlorophyll in leaves fades away and other leaf pigments like yellow and orange become visible. Depending on where you are in Wisconsin and what tree species are involved, we normally expect this color display from late September through October.

Trees showing color right now are much further along in the process than their green counterparts. Usually, the cause is either recent or chronic stress issues, leading to trees shutting down early. Drought typically tops the list of possible current issues, although most of Wisconsin has seen adequate rainfall in 2025. Keep in mind, however, it is possible for drought injury to linger and be a contributing factor even after rainfall returns, especially in higher stress locations or in trees already weaker for some other reason.

Most often individual trees that turn early every year have chronic root or trunk system problems reducing the flow of water and nutrients to leaves. Consider the fact there is often a delay between the cause of a problem and when symptoms, including early fall color, appear. Trunks with physical damage have reduced transport tissue, leading to lower food production in leaves, thus compromising tree growth and health. Likewise, as roots die away there is less support for the canopy of leaves above, so symptoms gradually occur sometime later.

Determining why specific trees show color early takes some detective work involving the site, along with trunk and root systems. Consider the location, as trees in stressful locations adjacent to streets, driveways, or buildings often show early fall color due to heat stress, restricted root zones, compaction, drier soils, and similar issues. In addition, trees impacted by construction activities in recent years commonly turn color early.

Examine trees for wounds, injury, or visible wood rot fungi growing out of the trunk. Wounds on trunks are best left alone but prune out any dead branches. Any large tree suspected of having structural problems should be inspected by a trained arborist, however, due to the risk of structural failure and subsequent potential damage.