BOISE, Idaho — Summer is over and fall is here, with all of the beautiful colors coming out on the trees and shrubs. But have you ever wondered just what makes the leaves change from green to those beautiful reds, yellows, and oranges?
Autumn weather has been slowly settling in across Idaho, and it's looking a lot more like fall every day. The leaves on the trees and shrubs have been changing from green to bright reds, oranges, and yellows. But cooler temperatures actually have very little to do with the onset of these fall colors.
Trees take up water from the ground through their roots and absorb carbon dioxide from the air. Along with sunlight and a chemical called chlorophyll, which gives the leaves their green color, the trees undergo a process called photosynthesis. The results is oxygen, which is released into the air we breathe, and glucose, the sugar which nourishes the tree and helps it to grow.
As the days get shorter, trees instinctively know that they need to get ready for the coming winter. With less sunlight, photosynthesis slows down, and the trees eventually stop making food, and the green chlorophyll begins to disappear from the leaves.
What's left is the yellows, oranges, and reds that were in the leaves all the time but we couldn't see them because of the green chlorophyll.
So, does the weather have anything to do with the leaves changing colors? Not really.
Leaves change colors because of the decreasing amount of daylight as the days get shorter. But the weather conditions can make a difference in the intensity of the fall colors.
In some years, those fall colors seem brighter and more spectacular than in other years. When we have a strong of warm, sunny fall days and cool, but not freezing nights, we tend to see more red colors. The leaves produce sugars during the daytime, but the cool nights lock that sugar in the leaves. Compounds called anthocyanins allow the trees to recover those nutrients before the leaves fall off, and they give the leaves their bright shades of reds and purples.
Yellow, gold and orange colors are fairly constant from year to year and are produced by a substance called carotenoids, which are always present in the leaves.
Different species of trees produce characteristic colors. Oaks turn red and brown. Aspens, poplars, and cottonwoods turn mainly yellow and gold. Maples turn bright orange and red. Honey locusts turn a brilliant gold.
Eventually, the base of the leave closes off, trapping the sugar in the leaf, and the leaf soon detaches from the branch and falls off.
Now the tree will go to sleep for the winter, living off the stored food it produced all summer long, until next spring, when the process starts all over again.
You don't have to go far to enjoy nature's colorful show. Down every neighborhood street, along the greenbelt, and in any park in town, you'll see a brilliant palette of fall colors in reds, oranges, yellows and gold.
If you're thinking about planting a new tree, now's the time to visit local nurseries and garden centers, because you'll be able to see what color that tree will be in your yard next fall and you can grow it.
Fall colors reached their peak in the high country over the last few weeks, and are peaking now at lower elevations, including here in the Treasure Valley.
A few of the best spots for leaf peeping include Kathryn Albertson Park in Boise, Scentsy Commons in Meridian and along Indian Creek in Caldwell. Don't forget to share your pictures of the beautiful fall colors on social media, especially on KTVB's 'Idaho Weather Watchers' and 'You Can Grow It' Facebook groups.
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