Why do the leaves change color?

Fall Color - San Juan NFFall Color - Medicine Bow NFMount Sneffels WildernessAs long, hot summer days and balmy evenings shift to shorter, cooler, autumn days and longer, crisp, cool evenings, deciduous trees prepare for a long cold winter.

The soft green palettes of summer transform into vivid autumn reds, oranges, golds, and browns. If you are lucky (really, really lucky!) you will witness that moment the leaves peak - a canvas of shining, brilliant gold. Three factors influence autumn leaf color:

  •   Leaf pigments

    • Chlorophyll gives leaves their green color. It allows plants to use sunlight to make sugars for their food they will use during the winter when they are dormant. 

    • Carotenoids produce yellow, orange, and brown colors.

    • Anthocyanins are the red, purple, and blue colors.

  • Length of days and nights

    • During summer, chlorophyll is continuously produced and broken down – hence the green leaves. As fall nears, days get shorter and nights get longer the production of chlorophyll slows down until it stops completely. Now the carotenoids and anthocyanins (hidden by the chlorophyll all summer) show through and display their colors.

  • Weather

    • Weather influences fall colors primarily during the time leaves are green and actively producing sugars. 

Certain colors are characteristic of a particular species. Aspen are predominantly yellows and golds, Maples vary species by species-and can display brilliant red or glowing yellow and every color in between. Remember deciduous trees are not the only things to turn color in the fall - look a little closer and you will see most plants getting ready for winter in some way or another.

Want More Detailed Information?

The Chemistry Behind the Beauty of Fall Colors