What causes leaves to change color?

Around this time of year many people will go on “leaf peeper” road trips to enjoy the changing fall foliage. While enjoying the colors, some may not know exactly why the leaves change their color. As temperatures cool, some plants stop making chlorophyll, the green pigment found in almost all plants. It acts like a solar panel, capturing energy from sunlight. The cells of the plant then use this energy to produce sugars to feed the plant. As days shorten from fall into winter, there is less sunlight for the chlorophyll to absorb. In areas like ours, it would take too much energy for trees to keep their leaves healthy, so in winter, deciduous trees drop their leaves and go into a state of dormancy.

As it gets colder, the tree will break down and absorb what chlorophyll is left and in its absence, the leaves will turn yellow, orange and red. Yellows and oranges are remaining pigments called carotenoids. The carotenoids are present all season but are hidden by the green of the chlorophyll. Reds and purples are the result of pigment called anthocyanin. Anthocyanin is produced in the fall as the glucose from the fading chlorophyll becomes trapped in the leaves. The amounts of these pigments and chlorophyll are all dependent on temperature, moisture and the amount of sunlight. As a result, each foliage season is unique because of these chemical changes inside the leaves. Every fall, the balance is different. Each new year paints a different, magnificent picture. So whether you go on a road trip to see the fall colors or just admire them from your own window, you can understand the complex chemical addition and subtraction that goes into the beautiful palette we get to enjoy for a fleeting moment.

Check out the colors at Wellfield (the above photo was taken this week in our Island Garden-spectacular!) during your next visit. We’re open daily, 10 a.m.-6 p.m. through October 31; starting November 1, we’re open 12-5 p.m., Tuesday-Sunday, closed on Mondays!

Amy Myers
Horticulture & Facilities Manager