This time of year we New Englanders are blessed with the gorgeous colors of fall. While there’s something to be said for simply enjoying the beauty of things without asking questions, I have an eight year-old son who needs to know why. So to understand why these vibrant colors emerge, we must delve into a brief science lesson. Don’t worry–I will make it as painless as possible.
A leaf's color comes from natural substances produced by plant cells called pigments. Leaves typically have 3 pigments, Chlorophyll (green), Carotenoids (yellow, orange and brown) and Anthocyanins (reds). By far, Chlorophyll is the most important pigment because without it the leaves wouldn’t be able to photosynthesize. Throughout the growing season green Chlorophyll is the dominant pigment, masking the other colors dwelling beneath.
Chlorophyll requires sunlight and warm temperatures (go summer!). So, when autumn brings its cooler temperatures and shorter days, Chlorophyll production becomes less and less until it finally stops all together.
Once the Chlorophyll begins to break down, this is an opportunity for the other pigments/colors to emerge. So, the combination of the green breaking down and the yellow, orange and reds emerging gives us a rich palette of color combinations.
There is some debate on what makes the best year for "reds". It is certainly weather dependent and a more in depth article to read further about the role of reds can be found at http://www.nature.com/news/2007/071029/full/news.2007.202.html.
Generally the consensus is that when there is plenty of moisture during the growing season, followed by a dry, cool and sunny autumn, we get the best conditions for the brightest colors. Whichever way it falls (pun intended), I am a grateful New Englander this beautiful time of year. And my son can consider himself informed enough to start raking leaves!