*October Highlight*

Every fall in Vermont the leaves of hardwood trees change from their steady old green color that we see through the growing season, to many different beautiful colors. Although almost all of us can say that it is a wonderful process to observe, we can’t all say we understand why and how it happens.

The change in leaf color is a result of chemical processes which take place as the days grow shorter and the nights grow longer and cooler.

The familiar green color we see in all leaves is actually caused by the pigment known as chlorophyll. Chlorophyll is necessary for photosynthesis, the chemical reaction that enables plants to use sunlight to manufacture sugars for their food. Trees in Vermont and all temperate zones store these sugars for winter dormancy. Most of the year colors we see in the fall are “hidden” by large amounts of chlorophyll.

In the fall, because of changing daylight hours and temperatures, the trees stop their food making process and these colors are “exposed”. These fall colors are a result of two other pigments; carotenoids which produce yellow, brown and orange colors and anthocyanins which produce a more reddish color. Both chlorophyll and carotenoids are present in leaf cells throughout the growing season. Most anthocyanins are produced in the autumn, in response to bright light and excess plant sugars within leaf cells.

Certain colors are characteristic of particular species. Maples differ species by species. Red maple turns bright scarlet or red, sugar maple turns a brilliant orange-red and silver maples turn yellow, while striped maple becomes almost colorless. Ash, birch, black cherry and aspen turn varying shades of golden yellow; beech become light tan; oaks turn red, brown, or russet; and hickories reveal a golden bronze.
      
                       

** If you have ideas for future highlights please send an email to acorn@forwild.umass.edu **