By Ranger Steve Mueller
Red Maples in swamplands are the first to show fall color. It is typical for stressed plants or weak dying plants to change color earlier. Difficult growing conditions in swamps are demonstrated by the red appearing first on the maples in standing wet conditions.
Sassafras trees show red or yellow depending on the amount of sugar, anthocyanin, and carotenes present in the leaves. Sumacs change early to become a beautiful crimson. At the equinox, color change picks up speed. Green still dominates the landscape.
Uppermost tree leaves change color first. Treetop leaves are exposed to chilling cold before more protected inner leaves. This results in color changes at the top first and is usually followed by leaf color at the tree canopy edge.
Fall breezes rustle leaves and we get to see the first colors in the wind drifting to the ground, as leaves break free. A few fall until a gust of wind fills the air with a couple hundred leaves. Cherries begin shedding leaves before many other species. Their leaves are not cherry red like the fruits but are yellow.
Aspen colors draw our attention as green and amber leaves quake in the slightest air movement. The leaves have a flat petiole that holds the blade to the stem. The flat petiole makes them quake easily. The movement captures our eyes and the sound of wind among the leaves draws attention. As fall progresses, aspens become beacons of reflected amber light in the setting sun. Amber aspens are like massive streetlights beginning to glow in the dimming evening woods.
Closer to the ground, dogwood shrubs are a deep dark maroon and raspberries are a rich red. Among the most brilliant fall colors are the Virginia creeper vines clinging to trunks of dead trees. They are exposed to full sun and have more sugar in the leaves. The exposure to sun aids pigment richness. The creepers that are more shaded from full sun are usually yellow.
Watch trees in various nature niche situations to discover subtle variations occurring where individual plants work to survive in their unique location. Discover trees of the same species with one growing in less ideal conditions and notice it changes color before others of it kind growing in better conditions.
Plants shed leaves in preparation for winter by producing an abscission layer between the petiole (leave stem) and the branch. This is a layer of large cells that seals fluid movement from leave to stem or stem to leave. If weather conditions prevent leaves from shipping sugars from the leaves before the abscission layer forms, sugar gets trapped and fall colors become more beautiful.
Large cells of the abscission layer create a weak area where the leaves separate from the tree to create colors in the wind when they fall.
Sugar maples hold leaves well and then suddenly drop them in a few days. Karen’s parents often visit for her October 20th birthday. When they arrive, the two maples by the house still have many leaves. Her parents are always amazed by the time they leave three days later that most of the leaves have been shed.
Oak trees do not form a good abscission layer. The result is many of the leaves remain on the tree into winter or even spring when new growth pushes the old leaf off. Sometimes oak leaves turn red but it is usual for them to simply brown. Enjoy the flitting and fluttering of colors in the wind, while taking notice of individual trees.
Natural history questions or topic suggestions can be directed to Ranger Steve (Mueller) at the firstname.lastname@example.org