The Science Behind Fall Foliage

October 21, 2016

The Science behind Fall Foliage

201209-w-fall-foliage-autumn-treeWe normally associate bright colors on plants with attracting pollinators, but the vibrant yellows, reds, purples, and orange that we see in fall foliage occur for a different reason entirely! The colors produced that we see in fall foliage are all linked back to the tree’s growth process. Temperature impacts the quality and duration of fall foliage, but what actually triggers the colorful display each season is light, and time of nightfall. The length of each day’s period of darkness is a signal to trees that winter is coming, and it’s time to stop the growing process due to inadequate light for photosynthesis.

Xanthrophylls, which cause yellow coloring, and Caortenoids that cause orange, are actually present in leaves throughout the summer- but the green caused by chlorophyll masks this. Once photosynthesis ceases, and the chlorophyll begins to break down in leaves, the yellow and orange are revealed! Red and Purple however, are actually produced during the fall. Anthocyanins are the chemicals that cause red and purple coloring in leaves, and they are produced through the glucose that remains after photosynthesis stops.

Eventually, just like the chlorophyll that preceded them, the chemicals that cause fall coloring will all break down, leaving only the tannins which are brown.

 

Why is fall foliage better some years than others?

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Sunlight, temperature, soil, and moisture all influence the quality and color, as well as the duration of fall foliage. We’ve broken these factors into ‘fall foliage formulas’ to help explain how certain factors make a difference!

 

Abundant Sunlight + Low Temperatures = Chlorophyll destroyed more rapidly.

Cool temperatures at night + Abundant sunlight = increased production of Anthocyanins

Frosty Nights = Destruction of the development of Anthocyanins

Drought During the Growing Season = Possible leaf drop before fall colors develop.

Ample Moisture During Growing Season + Dry, Cool, Sunny Fall with warm days and cool frostless nights = Brightest fall colors!

 

Looking to make the most of your property’s landscape all year round, and develop a beautiful fall foliage display in your own backyard? Check this Fall Color Guide to see which trees to plant to get your favorite fall colors!

Feel that your trees don’t seem to be producing the fall colors you remember, or perhaps seem as though they are declining? Contact us to set up an appointment for our Consulting Arborist to inspect the conditions of the trees and shrubs at your property!

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