Leaves changing color early: Is this a sign of things to come?

CLEVELAND - The leaves on some local trees are already changing color and its only mid-August. Many of you are sending me pictures of leaves turning from the classic mid-summer dark green to shades of orange and red. Is this a sign of an early fall, you ask?

Leaves change color normally in early fall in response to shortened amounts of daylight and colder temperatures. The green-colored chlorophyll breaks down, allowing the other chemicals in the leaves to stand out and show off their brighter colors. But that's in September and October.

I've noticed some leaf color as well. And yes, it is early for fall colors to show. So, what's causing the color change?

The first thing to note is that its not widespread. Its a few trees here and there showing color. The vast majority of local trees are green. That tells me the early color is likely due to plant stress. Trees can be weakened by a variety of natural and man-made factors.

First, excessive heat and drought can cause your trees to go dormant a bit prematurely. Excessive moisture can shut down a tree's photosynthesis as well. And yes, persistent cool temperatures can stop the sugar-making process in the leaves a bit earlier than normal. The stress can occur over several seasons or even several years. 

Insects and disease can also weaken a tree and cause early leaf color.

Man-made causes include disturbing the root systems of a tree for construction or landscaping.

My hunch is environmental stress over the past couple of years. During the summer of 2012, Northern Ohio touched 90 degrees or higher on a whopping 28 days. That's a lot of stress on all things outdoors. Then there was last winter. Four separate episodes of temperatures dropping to between -10 and -15 degrees. Many trees suffered bud damage from last winter's frigid temperatures. So, tree stress has been a common thing across Northern Ohio the last couple of years.

Not to worry, though. The majority of our trees will begin to change colors in September, right on cue.


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