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Early fall color could be a sign of tree stress

a sweetgum tree beginning to change to a red fall color

As summer transitions to fall, many Illinoisians are looking forward to everything pumpkin-spiced, hoodie weather, and the fall color of our trees. However, even at the tail end of summer heat, there are trees already rewarding us with some fall color. But is it a reward or a call for help?

Some trees are quick to turn and drop their leaves in the fall. At this point though (early September), it is still too early for trees to begin to change. In 2023, peak fall color for Central Illinois is predicted to start October 15. So why are some trees changing now? Very often, the reason is the tree is under stress.

While many stresses can affect a tree to initiate early fall color, drought is a common culprit. 2023 has been a time of drought in Illinois. Particularly for our trees. In the spring of 2023, we experienced a spring drought, which is fairly rare for Illinois. July brought much-needed rains, but the dry weather returned in August. We have also had a recurrence of fall droughts in recent years that put our trees in a water deficit as they go into winter dormancy.

I have noticed many of the earlier fall-colored trees, like the white ash in my front yard, already changing and dropping leaves. I am aware of my ash tree’s history, therefore, know it is overall very healthy and protected from emerald ash borer. Therefore, the drought is a likely contributor to its early fall color.

Yet, during a recent walk around Galesburg, Illinois I spotted several trees with early fall color that are suffering from things beyond the drought. So if you are seeing trees with early fall color, here are some possible issues beyond drought that can be the cause:

  • Do you see a root flare at the base of the trunk? The root flare is where the trunk flares out into the root system and should be above the soil line. Trees planted too deeply often slowly succumb to rot at the base of the trunk. This can take a decade or longer to manifest as a problem after planting.
  • Do you see any damage around the base of the tree? The tissue that moves water and nutrients up and down the trunk is right behind the bark. When equipment like a mower cuts into the bark and the tissue behind it, that severs the connection to the roots and canopy. Keep in mind trees do not heal, they seal. So that connection of tissue is damaged for the rest of the tree’s life.
  • Do you see any roots circling the trunk? Trunk tissue is different than root tissue and the two will not graft or grow into each other. Therefore, a circling root will slowly strangle a trunk, eventually girdling and killing the tree.
  • Has there been any construction in the root zone? The loss of roots from construction often creates a delayed reaction of canopy loss over several years. Trees react to damage more slowly than people expect.

It doesn’t have to be the end of the growing season for a stressed tree to exhibit early fall color. Stressed trees can show the fall colors in spring or summer too. It’s always a good idea to inspect trees turning color when all other trees are remaining green. Certified arborists or your local Extension office can assist with questions on tree health.

Good Growing Tip of the Week: Mulch is very beneficial to preventing drought stress on our shade trees. Mulch 2- to 4-inches deep and avoid piling mulch against the trunk.

Thank you for reading!

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Chris Enroth is a horticulture educator with University of Illinois Extension, serving Henderson, McDonough, Knox, and Warren counties since 2012. Chris provides horticulture programming with an emphasis on the home gardener, landscape maintenance personnel, and commercial landscapers. Additional responsibilities include coordinating local county Master Gardener and Master Naturalist volunteers - providing their training, continuing education, advanced training, seasonal events, and organizing community outreach programs for horticulture and conservation assistance/education. In his spare time, Chris enjoys the outdoors, lounging in the garden among the flowers (weeds to most).