Why are your leaves changing color in the fall?

Fielding Tree and Shrub Care - Why do trees turn colors in the fall?

Fall in Colorado is a beautiful time to enjoy the crisp air, roast s’mores over a fire pit, and watch the leaves turn red and gold.

Do you wonder why leaves change color? Is it because they’re dying? You may be surprised!

Healthy leaves are usually green and flush with strength through the spring and summer months. As the weather turns into fall, the amount of daylight starts to shrink. We adjust our clocks for daylight savings, but trees go into survival mode. Trees understand that having less sunlight and colder temperature means that winter is coming. They stop producing chlorophyll, a green pigment that helps convert sunlight into nutrient-rich sugars through photosynthesis.

What’s amazing is that chlorophyll also masks the true color of some leaves. When the tree stops making chlorophyll, the green pigment of the chlorophyll starts to break down. This exposes the true pigment of the leaves that remains.

One of the most common misconceptions about leaves changing colors is that the yellow and red colors are the chlorophyll changing color as it breaks down. The yellow color of leaves are actually that color all the time, but we can’t tell they’re that color because they’re filled with green chlorophyll. When the chlorophyll stops filling the leaves, the real color is brought to light and makes Colorado look even more beautiful in the fall. Leaves that turn red are because of another exciting biological change that happens in the fall.

Why do leaves turn yellow in the fall

If a leaf is more yellow or orange in the fall, it’s rich with carotenoids. This is the same pigment that’s found in carrots, pumpkins, egg yolks, and bananas. It’s a natural coloring that starts to show its presence when a plant has reached its end of maturity, like a banana turning yellow or leaves turning from green to gold.

Carotenoids are a part of leaves all through the growing season. Most of the tree species that are native to Colorado, like aspens, are heavy with carotenoids. When the aspens turn yellow across the Front Range and in the mountains, it’s because they know winter is coming and we see their golden beauty. You can read more about aspen fall colors from the Colorado State Forest Service here.

Why do leaves turn red in the fall

If a leaf is reddish in color, that’s because it contains more anthocyanin. Unlike carotenoids, anthocyanin is not present in leaves throughout the growing season. It’s only towards the end of the summer that anthocyanin begin to be produced. When the tree stops producing chlorophyll, it alerts the tree to synthesize anthocyanin to replace the chlorophyll. Anthocyanin is actually a toxic pigment that helps protect the tree from bugs as the tree is more vulnerable heading into winter.

A wetter summer and cooler fall weather help keep trees flush with color. If you’d like to see Colorado’s fall colors, Channel 7 News shared a list of great places to see fall colors in Colorado.

Fall is a prime time to check your trees before winter hits. Fielding Tree and Shrub Care provide tree care in Littleton, south Denver, Parker and across Douglas County. Click here to schedule a complimentary estimate.