The Science of Fall Color
As the air cools and the days shorten, trees begin a quiet transformation that turns science into art. You learned – probably as early as elementary school science class – that plants are green because they contain chlorophyll in their leaves. Chlorophyll absorbs red and blue wavelengths of light for photosynthesis and reflects the green wavelengths we see in the color of summer leaves. Today, we will explore why the greens fade and just where the red, orange, and yellow colors of fall leaves come from.
The Chemistry Behind Fall Color
Chlorophyll is most actively produced in bright light and warm temperatures. As summer turns to fall, with its shorter days and cooler temperatures, chlorophyll production decreases, allowing another pigment, carotene, to take the stage. Carotene absorbs green and blue-green wavelengths, making yellow wavelengths visible in reflected light. This pigment lends the golden hues we see in birches, hickories, and Prairie Gold® aspen.
The purple, red, and orange hues characteristic of fall are a result of a family of pigments called anthocyanins, which are produced within the leaf as days shorten and sugars accumulate in the leaves. The presence or lack of anthocyanins is dependent upon the species of tree or shrub.
Why This Year’s Fall Colors Are Especially Vibrant
If you’ve stepped outside lately, you’ve probably noticed something special — Nebraska’s trees are putting on one of the most colorful shows we’ve seen in years! Across Lincoln and much of southeast Nebraska, canopies are glowing with golds, reds, and deep oranges that seem almost electric against the clear October skies.
So what’s behind this radiant burst of color? In short: healthy trees, replenished soils, and a little help from the weather. When fall arrives, trees stop producing chlorophyll and begin reabsorbing nutrients before winter dormancy. This year’s healthy summer conditions allowed trees to build plenty of sugars and pigments in their leaves.
A “Drought-Busting” Summer Set the Stage
After several years of dry conditions, this past summer brought the rainfall our landscapes had been waiting for. It was the wettest summer in several years statewide. At the beginning of June, nearly 85% of Nebraska was in drought. By early fall, less than 20% remained so — and some regions saw four-category improvements, moving from extreme drought to “nil.” And September kept the trend going! Lincoln recorded 3.53 inches of rain, the wettest September since 2019, compared to the 0.8-inch average from 2020–2024.
That shift in moisture makes a big difference. As Michigan State University Extension notes, consistent soil moisture throughout the year often leads to more vivid and prolonged fall color displays. When trees aren’t fighting drought, they can focus on color chemistry instead of survival. And when combined with warm days and cool nights, those pigments, especially the anthocyanins (reds and purples), shine brighter and last longer.
A Perfect Time to Plant!
If you’re planting trees this fall, you’re right on time. The same cool nights and mild days that make for great color also make for excellent planting conditions. Moist soils and reduced stress help roots establish before winter — ensuring your trees are ready to burst with life (and color!) next year.
