Autumn brings changing leaf colors. Many travelers flock either to the southeast or New England where the predominant tree species produce nature’s gems of gold, orange, red and burgundy. Photosynthesis produces the chlorophyll that makes leaves green during the growing season. Color change is initiated by longer, cooler fall nights which cause photosynthesis to slow and then stop. Hue intensity varies from year to year. Plentiful summer rains allow trees to retain their leaves longer, resulting in better colors.. Conversely, summer drought can cause premature leaf shed and little to no color.

Different autumn hues are caused by three pigments: carotene, xanthophyll and anthocyanin. If you read last week’s blog on pumpkins, you recognize carotene as the substance that makes pumpkins orange. It also gives Sugar Maples their fabulous orange fall color. 

Xanthophyll produces yellow leaves, seen in aspen, beech, catalpa and hickory trees.

Anthocyanin produces red leaves. It differs from carotene and xanthophyll because it requires sunlight for production. Color concentration is enhanced by cold, sunny days. This substance gives red maples, red oaks, tupelos, sourwoods and sweetgums their rich rosy hues.

Some of my favorite plants show all the fall colors. Persian Ironwood (Parrotia persica) and Fothergilla put on a multi-hued show every fall. In the Mary Snoddy garden, a sweetgum and sugar maple grow shoulder to shoulder next to a large Southern Magnolia. The red of the sweetgum looks even more robust in contrast to the warm yellow-orange of the maple. Both colors look more intense in contrast to the deep green of the magnolia. Outside the local library, a Kousa dogwood shimmers with intense colors.

Fall colors are at the brightest when the weather pattern has included a warm, rainy spring, and sunny fall days with cool nights. All the colors look wonderful against the brilliant blue of autumn skies.