- Author: Janet Hartin, UC Cooperative Extension Environmental Horticulture Advisor
Published on: November 26, 2022
![Colorful trees in autumn line the edge of a parking lot.](https://ucanr.edu/blogs/Green/blogfiles/96203small.png)
"Green, yellow and orange colors are always present in leaves, but chlorophyll – the green pigment responsible for photosynthesis – is so dominant during most of the year that it masks out the other colors," says Igor Lacan, UC Cooperative Extension urban forestry advisor.
Did you ever wonder why trees "turn" color in the fall? The short answer: It's primarily a function of long, cool fall nights and short, sunny days.
The longer answer? Chlorophyll is responsible for the basic green color of leaves we see in spring and summer and is a necessary component of photosynthesis, which uses sunlight to manufacture sugar (food) that is stored during the dormant period of the year. Carotenoids produce yellow, orange and even brown pigments in crops such as carrots, squash, bananas and many ornamental plants such as daffodils and poppies. Anthocyanins are red and orange in color and are most linked to lavish displays of brilliant fall foliage. They also...
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