Every autumn, nature reveals its beauty in the vivid, colorful leaves all around us. With orange, yellow, red, and golden leaves changing in each passing day, we start to think of the reason behind this spectacular phenomenon that happens every year. Why do leaves change colors and fall to the ground every autumn? Some may think it’s because they die, others think it’s due to the changing temperatures, or they may think it has to do with less sunlight. It’s safe to say that two of those answers play a role in the changing leaves. Although it might seem that trees drop their leaves every year because they die just to grow new ones each spring, that is not the case. Instead, trees and leaves undergo a process every year in order for them to prepare for winter.
Leaves that we observe during fall have bright colors embedded in them all year, but we don’t see it during summer because chloroplasts in trees produce a lot of chlorophyll in which the green pigment overpowers the other colors. Chloroplast are organelles in leaf cells that are responsible for photosynthesis, which is the conversion of light into energy It provides the energy that the tree needs to grow big and strong. Chlorophyll, as you may have guessed, is the green pigment we see in leaves during spring and summer and the pigment that dominates most. Other pigments are also in leaves, but don’t get to show their colors until cooler temperatures and less sunlight arise. Carotenoids and xanthophylls are the orange and yellow pigments respectively while anthocyanin are the pink, red, and purple pigments.
The reds of a maple tree are often striking.
As summer now turns into fall, temperatures start getting colder, and our sunlight seems to be slipping away from us, we look to the changing leaves and wonder, how? In the colder months, instead of holding onto its leaves, trees will drop their leaves to save energy. Because there is less sunlight, trees stop making chlorophyll. The chlorophyll still there will start to break down. Instead of making chlorophyll from scratch every year, trees will reabsorb what is left of chlorophyll and use it in spring once buds start to form. Once there is no more chlorophyll left, the other pigments will start to show through: reds, oranges, and yellows.
But if they don’t die, how do they fall off the tree?
Leaves don’t just fall off the tree or get blown off by wind. Deciduous trees will use a technique in which they just throw their leaves. The word deciduous means to “fall off.” These trees have cells that act like scissors. The cells will use this technique to slowly build up a bumpy line that pushes the leaf off the tree. Once the leaf falls, the tree will seal that spot to prepare for winter. It is very important for the tree to seal off the spots. In summer, the tree loses a lot of water through holes in the leaves. If the tree does not seal those spots come winter, the tree will dry out and die. Because trees do seal off those spots, once spring and fresh water arises, new buds will be able to grow with plentiful of water and the chlorophyll that the tree absorbed in the fall, turning them bright green.
How can we enjoy beautiful fall colors in the Cerro Gordo County Area?
Basswood trees are beginning to show their yellow foilage.
Start by going onto the Cerro Gordo County website. Under departments, and under conservation, choose Things to Do. Once there, scroll to the bottom and choose the Nature Viewing folder and then the Fall Colors Brochure. The brochure gives you a suggested fall colors scenic drive where you can drive from one place to another or stop and walk the trails for a closer view. Here in northern Iowa, our “expected peak” is the first two weeks in October. But don’t be fooled, depending on the weather, the peak can come sooner or later.
You can also check out the Iowa DNR page online where they keep us updated on where colorful displays are located throughout Iowa. They also post when the expected peak is. If you are wanting a more specific color, here are some common deciduous trees that provide you with the color of your choice.
Ash: yellow
White Ash: yellow/orange with a purplish tint
Elm: yellow
Hickory: yellow
Maple (soft): yellow
Maple (hard): red
Bur Oak: yellow
Red Oak: red
White Oak: purple
Marie Maston is a naturalist intern at Cerro Gordo County Conservation.
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October 10, 2020 at 09:00PM
https://globegazette.com/news/local/why-do-trees-turn-red-and-yellow-in-the-fall-and-where-in-north-iowa/article_3617eb05-3ba1-5c6e-92ed-a6aad9ed2836.html
Why do trees turn red and yellow in the fall, and where in North Iowa can I see them? - Mason City Globe Gazette
https://news.google.com/search?q=Red&hl=en-US&gl=US&ceid=US:en
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