DES MOINES, Iowa — If you think this fall is more vibrant than past years, you would be correct. Experts say Iowans will see more vivid colors in the trees.
Each year as summer transitions to fall, Earth also begins to tilt away from the sun. That means less daylight in Iowa. The sun, of course, is what feeds the trees. Within the leaves is a pigment called chlorophyll. Chlorophyll uses the sunlight to convert carbon dioxide and water into oxygen and sugars, which give the tree energy. Chlorophyll is what also makes the leaves green. During the summer, chlorophyll dominates over other pigments like carotenoid and anthocyanin, which make the leaves yellow, orange and red. But when fall rolls around, less sun means less chlorophyll.
“They change color because this time of year the tree starts shutting down and there’s not as much chlorophyll being produced. That leaves behind some of the other things that we don’t normally see in the leaves like the carotenoids, which should make them yellow and orange,” said Emma Hanigan, the Iowa DNR’s state urban forester.
The other pigments will finally get their time to shine, and this year, that color is even brighter.
“We see more vivid fall color when we’ve had a drought like we had this year. That’s because there’s a lot more sugar stored up in those leaves, and then oftentimes if we have a wet fall while the leaves are changing, they will just drop to the ground and we won’t be able to see that full spectrum of colors,” said Hanigan.
Like the wet fall conditions, a hard freeze would also mean the end to our fall colors. However, we will be far from freezing temperatures over the next seven days, which means plenty of opportunities to check out this year’s colors.
“In our urban areas we have mostly maple. About a third of our trees are maple. Then another 17 percent, while this is changing, are made up of those ash, so the green ash, which is yellow and fall color and then the white ash, which is a nice purple,” said Hanigan.
Fall is also a good time to plant trees because the warm soil will help the roots become established before the ground freezes.