These articles are written to apply to the northeastern corner of Illinois. Problems and timing may not apply outside of this area. Now that fall has arrived and cool weather is back, trees will be turning color.
Trees turning brilliant color is one of the highlights of the fall season.
How this occurs is often misunderstood, however. While actively growing, leaves on trees are green because chlorophyll is abundant inside them. Other color pigments are actually present, but are hidden by the chlorophyll. As the season winds down and days get shorter, chlorophyll production in leaves slows down as trees and shrubs prepare for dormancy. Once chlorophyll breaks down in the leaf, other color pigments in the leaf become visible.