The leaves are changing and the wind is taking them off the trees. Some of the beautiful colors that frame walks in the arb these days are coming from sugar maples (Acer saccharum) and Red Oak (Quercus rubra) trees. Sugar maples and red oaks are easy to spot these days, with the bright colored leaves. Sugar maple trees have leaves with five lobes with smooth or wavy-pointed edges. Red Oak trees have alternate, simple leaves with seven to eleven lobes that are only cut to half of the middle of the leaf.

While it seems like each tree is on their own schedule, the color change in leaves comes from a decrease in temperature and daylight. In the summers when the days are long, chlorophyll is constantly being broken down and produced, and as a result we see green leaves. But in the autumn when the days become shorter chlorophyll production decreases, eventually stopping. This makes way for the other pigments in the leaves to be revealed and we see wonderful fall colors. Sugar Maple leaves often turn red first, then orange and then eventually to yellow. Red oak trees have russet-red leaves that take a while to fall.

Fallen leaves are not meaningless dead leaves, they will decompose and nourish the soil. These leaves make up the spongy humus layer of the forest floor that holds in rainfall. These fallen leaves can also be food for numerous forest organisms that make up the forest ecosystem. It is a beautiful time for a walk through the arb as these trees prepare to survive the cold winter and the colorful leaves blow in the wind and begin to litter the ground.