Weather and environmental factors in early fall leaf color changes

SOUTH BEND, Ind. -- Fall is approaching, but some of the signs of the season are showing prematurely. Michiana has just emerged from the infamous “false fall,” experiencing several days of cooler-than-average temperatures, also accompanied by dry conditions.

Mark Evans, Plant and Soil Educator at the Purdue Extension Office, explains how weather plays a significant role in how and when leaves change during the fall months.

Evans says, “Shorter day length, longer nights, is what actually causes us to have the fall color.” Frost or freeze is not ideal, he explains, but cool nights, warm days and moisture are what will bring the vibrancy for fall.

As we receive less sunlight, it signals the leaves to stop producing chlorophyll—the compound responsible for their green color. Once chlorophyll breaks down, the leaves begin to reveal their natural pigments of yellow, orange, and red, creating the vibrant fall scenery many look forward to.

Cooler temperatures can speed up this process. Meanwhile, drought conditions dry out leaves, causing them to turn brown. Prolonged periods with little to no rain, Evans explains, can also affect the vibrancy of fall colors, making them appear dull or faded.

According to Evans, areas that have received steady rain will likely see the most vibrant displays. For those in dry regions, he suggests watering trees to help them stay on track for fall.

Weather isn’t the only factor. Bill Zimmerman, local arborist and owner of American Tree and Lawn Care says that premature color change is often a key indicator that something within the tree’s system is malfunctioning or damaged. Root damage—often caused by construction or changes in elevation—is one of the most common causes.

Other red flags include bark peeling off the trunk or mushrooms growing along the base of the tree. If these symptoms are caught early, professionals may be able to step in and help restore the tree’s health.

Zimmerman encourages residents to keep a close eye on how their trees are progressing this season.

Recognizing the signs of early color change in your own yard can be crucial. If you're already noticing yellow or orange leaves, it might be time to take action to protect your tree’s health.