How Trees Get Their Fall Colors

It feels like just yesterday summer showed up and now its fall and October is here and is leaving me wondering just where has 2016 gone? Cooler days means it's easier to work in the yard and of course being outdoors means we can enjoy the gorgeous colors of fall.

How plants get their fall coloring is quite interesting. The green you see in tree leaves comes from chlorophyll. Throughout the year, that chlorophyll is constantly being broken down and replaced and so the leaves appear green. Chlorophyll is necessary for photosynthesis to occur within the leaves which is the process that allows plants to produce sugars. Within those leaves are also xanthophylls and carotenoids which are attributed to yellow and orange colors – think carrots or daffodils. Another pigment in plants is called Anthocyanins which provides colors such as red, purple, and crimson colors – think strawberries or blueberries.

Chlorophyll, xanthophyll, and carotenoids are present in leaves all season long, but for many anthocyanins don't show up until autumn when there are excess sugars in the leaves of plants. As we crawl into autumn, nights are longer and chlorophyll production slows down and eventually stops and the remaining chlorophyll in the leaves is destroyed. Once chlorophyll is destroyed it allows the underlying pigments to come through.

Often a question arises what causes a good show of fall colors and it's attributed to weather conditions, temperatures and moisture being the top two impacting factors on fall color. Warm, sunny days and cool evenings lead to a better fall color display for our red, purple, and crimson colors. During the day there is a lot of sugars being produced, but at night with cooler weather, the veins in the leaves begin to constrict and reduce the amount of sugars that can exit out of the leaves. Anthocyanins are produced from the excess sugars in the leaves which mean we see more variability of those reds, purples, and crimson from year to year. Since xanthophyll and carotenoids are always present in leaves, yellows and orange fall color are more consistent year to year.

Drought can reduce fall color display as it can cause leaves to fall sooner than they are able to produce fall color and frost can destroy the parts of the leaves that produce anthocyanins. If you wonder when you will see our best fall color display, we want to have adequate summer moisture followed by an autumn with sunny days and cool evenings.

I've already begun to see the colors in leaves begin to change and look forward to seeing what our fall color display brings this year.