fall leaves coloring page

Why Do Leaves Change Color in the Fall?

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Video Transcript:

Hey there friends. I’m Yvonne Page Illustrates, and this is Facts to Relax, the show where I research a topic I find interesting and share the information I learn with you while coloring a picture on the screen. If you want to color along with me you can do so by printing the coloring page using the link in the description below. All coloring pages are free with no strings attached and are for both kids AND adults so by all means, color away with me!

Today we’re going to be answering the question of why leaves change color every year in the fall. In the northeast United States where I’m from, autumn means leaves on trees turning from shades of green to gorgeous hues of oranges, reds, and yellows. It’s a spectacular thing to witness and is one of nature’s greatest gifts, a final hurrah before plunging us all into months of darkness and seasonal depression. Long before scientists knew the reasons for this phenomenon, humans came up with creative stories to explain the changing foliage each year.

The Wyandot Indians told a story of a fierce battle between the Bear and the Deer up in the Land of the Sky which dripped both of their blood down onto the earth, coloring the leaves below crimson, red, and orange. Each autumn, the legend claims, trees turn these shades of red again to remind us all of that fateful and bloody battle.

Another tale told is of a sparrow who attempted to make his home in an oak tree. When the oak tree pushed him away, he tried a maple tree. Once again, this tree kicked him out as well. Finally, the sparrow landed in a pine tree that welcomed him. The creator looked down and saw the three trees’ behaviors and decided as a reward for housing the sparrow, he’d allow the pine tree to keep its leaves but punish the oak and maple trees for their cruelty by making them lose their leaves each year. 

There were not only legends about why the leaves changed colors, but also folklore about what different patterns of change might mean. For instance, one such supposition was that the earlier the fall colors peaked on the trees, the milder the winter would be and the brighter the leaf colors were, the harsher the winter would be.

Since the time when these stories were told, science has had a chance to come up with some other…well…scientific explanations of the phenomenon and I’ll explain that to you now.

Let’s begin with trees themselves. For the purpose of this video, trees can be split into two types: deciduous, which are essentially giant leafy flowering plants that lose their leaves, and evergreens, which have needles and keep them year round. Deciduous trees are the ones whose leaves change color in the autumn and then fall off. Some examples of these are birches, aspens, maples, oaks, elms, and beech trees.

All of these trees produce a chemical pigment called chlorophyll. Chlorophyll is what makes tree leaves and other plants green but, more importantly, it’s what absorbs sunlight and water and helps the plants during the process of photosynthesis. Photosynthesis is the process through which plants use sunlight to turn carbon dioxide and water into food. Every plant that uses photosynthesis has chlorophyll to assist in this process. Now as long as there’s a lot of light to absorb, Chlorophyll can work its magic and the tree stays fed and the leaves stay green but as the days get shorter and light gets weaker, trees go into energy saving mode and stop producing so much chlorophyll. The leaves, in turn, lose their green pigmentation before finally dropping to the ground as the tree no longer has enough energy to sustain them through the cold and dark winter. This is basically the plant version of hibernation, though in plants it’s technically called “going dormant.” 

Chlorophyll, however, is only half the story because it’s not so much the lack of it that makes leaves turn other colors. If it was all about the chlorophyll, leaves would just fade lighter and lighter green until they fell off. No, what’s actually happening is there’s another class of chemical pigments in these leaves as well, called Carotenoids. They also assist in photosynthesis, deactivate free radicals, and produce yellow, orange, and red colors. Now these carotenoids are always in the leaves but chlorophyll’s bright green color prevents them from shining through until the chlorophyll starts to die away. Different carotenoids produce different colored leaves. Carotene, which is also found in carrots, makes sugar maples bright orange. Xanthophyll turns beech, ash, birch, aspens, and some oak trees yellow. 

In addition to Carotenoids, Anthocyanin is another chemical structure found in some trees that, while not present in the leaf the whole time like carotenoids are, is produced when chlorophyll is breaking down and it’s responsible for those bright, brilliant red leaves you see on some trees like red maples, scarlet oaks, and red sumacs.

Finally, you may be asking, why don’t the leaves from evergreen trees change color and fall off like they do from deciduous trees? Evergreen leaves are rolled up tight like needles, rather than flat and wide like deciduous trees. These needles are also covered by a waxy coating. Both of those things help the tree conserve water, allowing them to continue to photosynthesize and hold on to the leaves longer than their deciduous cousins. That being said, the needles from these trees do eventually change colors, usually to a yellow or brown, and then fall off. They discard the oldest needles each year and grow new ones at the tips of their branches. Most needles live for about two to four years before dying off. Some evergreens drop their needles in the late summer or fall but others drop their needles in the springtime or early summer and the loss of needles is more noticeable in some trees than in others. If they’re cut, like in the case of Christmas trees, the needles will quickly start to fall off.

So there we have it. The answer to the question “why do leaves change colors?” as well as the bonus question “why do leaves fall off of trees in the winter?”

If you’re interested in learning more about the science behind trees and the changing of the seasons or want to read the myths I mentioned in the beginning, I suggest you check out the links in the Sources & Resources section of the description below. 

Thank you so much for stopping by and learning something new with me today. If you want to learn more new things with me, please consider subscribing to this channel and checking back often. Thanks again for being here to color and chill with me today and I’ll see you again soon! Bye!