People come from all over the world to NH during foliage season. It seems that our forests have just the right combination of species comingled with just the right climate. Some years are better than others of course. As the days get shorter, there is insufficient sunlight for photosynthesis and the trees prepare to 'rest' for the winter.

 
 
 
 
 

Leaves contain three pigments, chlorophyll, carotenoid, and anthocyanin. Chlorophyll provides the green, masking the other two pigments during the summer. During 'rest' the trees halt their chlorophyll production, allowing the other colors to shine!

 
 
 
 
 

Warm, sunny fall days, with above freezing nights still produce sugar in the leaves however cool night temperatures prevent the sugar sap from flowing through the leaf veins and down into the branches and trunk. The trees produce extra anthocyanin to help facilitate the collection of the sugar.

 
 
 
 
 

Carotenoid produces the yellow, orange, and brown colors and that pigment is fairly constant in the leaves. Variable anthocyanin provides the reds and purples. When Mother wishes, we get a better foliage season. Ideal conditions for amazing fall foliage include a warm, wet spring, a summer that's neither too hot or too dry, and a fall with plenty of warm sunny days and cool, but not freezing nights.