What Makes the Leaves Change Color Every Autumn?

The Science Behind the Leaves Changing Color

How beautifully leaves grow old. How full of light and color are their last days.

- John Burroughs

Hello Leaf Peepers! Do you ever wonder why some trees change to different colors in Autumn?  They mostly all start off as green, right?  So it would only make sense to have them all turn the same color as the weather turns. 

There is an entire science behind the changing of the leaves each and every autumn.  A tree’s location, temperature, light it receives (both natural and artificial), the amount of water all play a part in determining a tree’s autumn hue and just how long we get to enjoy its colorful display, and the actual intensity of its color.  All green plants contain chlorophyll which is an antioxidant-rich pigment.  Healthy plants in the summer are green, until the conditions around them change.  Temperature, water, and the environment all affect plants.   Different species of trees carry different pigments, and thus result in different colors as they transition from summer to winter.

Ideal conditions for the most colorful autumn are a warm and wet spring, a temperate summer (not too hot or dry), and an Autumn with a balance of warm days and cool evenings.    Depending on the balance of the pigments within the type of tree, and their reaction to their environment will determine the color in which a tree turns.

Types of Tree Pigments

Chlorophyll (Green)

Chlorophyll, as already mentioned,  is the tree pigment that makes the leaves appear green in the summer.  Chlorophyll takes the light from the sun and turns it into sugar.  This acts as the tree's main food source throughout the growing season.  While all trees host multiple pigments,  chlorophyll is a tree's dominant pigment that acts like a blanket over the other pigments in the tree in the summer.  Summer is the peak feeding season and masks the other colors that are in the tree.  At a certain point, the tree will stop making chlorophyll and create a “seal” between its leaves and the branches of the tree.  This is in order to conserve a tree's energy and food as it prepares for winter. When there is less chlorophyll in the tree (the green blanket pulls away) allowing the other pigments that are present in the tree appear more prominent, giving their formally green leaves their new autumn color.  Roots and branches can survive through the cold winter season, but leaves cannot, so they will eventually fall from the tree, as they are no longer being fed from the tree.  

As the days become longer, and as winter turns to spring,  there is more sunlight.  With this change, a tree will once again begin to absorb the molecules that make-up chlorophyll, and new leaves will begin to grow. 

Xanthophylls (Yellow)

Xanthophyll is a light-harvesting pigment, and what chlorophyll cannot absorb, xanthophyll can. Its main function is to protect the leaf from absorbing too much light which can cause damage to the plant. A dietary source of xanthophyll is lutein - which is found in the yellow in egg yolks and in corn, and yellow and orange fruits.  It has strong antioxidant properties.

Carotenoids (Orange)

Carotenoids start degrading in the leaf at the same time as chlorophyll, but do so at a much slower rate. Carotenoids, with the most common being beta-carotene, absorb blue and green light, and reflect red and yellow, thus causing the leaves to appear orange in color.  This pigment is also why carrots are orange.

Anthocyanins (Pink, Red, Purple)

Anthocyanins react with the change into fall weather.  Sugar gets trapped in the leaves of the tree causing a unique chemical change turning leaves red and even purple.  This is more common in trees like Dogwoods and Oaks.  Anthocyanins help protect trees from excess light and prolong the time that leaves fall from the trees.

Tannins (Brown)

Tannin is a brown pigment that, though dull in color, has a very important role in the life of a tree.  It protects the tree and its leaves from fungus or bacteria. It is astringent, and is used in skincare, as it tightens pores and draws out liquids, much like its process when protecting a tree. It is the last pigment to break down in a leaf before it falls.

Want to know what types of trees turn what color?   

Are any of these trees in your yard?

Maples - depending on the type of maple, they turn yellow, orange, and red

Serviceberry - orange and red 

Sweet Gum - gold, red, pink, purple - sometimes on the same tree

Honey Locust - yellow 

Green Ash - yellow 

Hackberry - yellow

Sumacs - red, gold, orange

Poison Ivy - orange, red, purple

Virginia Creeper- red

Dogwoods - red, or purple

What Do the Colors Of the Leaves Mean?

Every color has a wide range of symbolic meanings depending on the context or the environment the color is found in.  In leaves, the color represents the following if you are an appreciator of the fall season.  

Green Leaves: growth, harmony & health 

Yellow Leaves: happiness, positivity

Orange Leaves: warmth, enthusiasm, optimism 

Red Leaves;  strength, energy, confidence 

Brown Leaves: comfort, stability, honesty

Green Is Good

Not all trees change their color from green to varying shades of the rainbow, and if they do, it is more likely that they are dying or sick. 

Here are a few trees that stay green all year:

• Pine Trees
• Fir Trees
• Spruce Trees
• Cedar Trees

Embrace the Season!

Here in the Kansas City Region,  our Fall colors from the autumn leaves are beginning to intensify with fall foliage reaching its peak color very soon.  Our dry weather of the past few months has caused many trees to already turn brown and drop their leaves, but there is still plenty of color and visual splendor to be had in our area.  So spend one of the last sunny afternoons of the season to take in all of nature’s splendor.  There are plenty of places all around to appreciate nature’s colorful display. Peak season isn’t here quite yet, but it will be gone before you know it!  See below for some places to take in the sights!

Some Great Spots for an Autumn Hike

• Legacy Park Loop, Lee's Summit
• Burr Oaks Woods Conservation Area, Blue Springs
• White Alloe Creek Conservation Area, Parkville
• Maple Woods Natural Area
• Thomas H Swope Memorial
• Weston Bend State Park
• Cliff Drive Scenic Byway, near Kessler Park
• Powell Gardens

A Final Thought

Though some people may not appreciate the "aftermath" of fall leaves - (hello raking!) a drive through your community appreciating what the season has to offer, may just have you changing your mind, at least for a little while.

Anyone who thinks fallen leaves are dead has never watched them dancing on a windy day.

- Shira Tamir