How cooler temperatures will impact fall foliage in the Commonwealth

ROANOKE, Va. (WFXR) – As the Commonwealth prepares for cool temperatures to start moving into the month of Nov., these temperatures could affect the stunning, local fall foliage around the state.

According to the U.S. Forest Service with the Department of Agriculture, there are three main factors that influence autumn leaf color, leaf pigments, length of night, and weather. The timing of color changes and the onset of falling leaves is primarily regulated by the calendar as nights become long. As days grow shorter and nights grow longer and cooler, biochemical processes in the leaf begin to change its color.

Fall foliage can best be seen during a succession of warm, sunny days and cool, crisp but not freezing nights. The chemical process works during these days due to the high amounts of sugar produced in the leaf. During these cool nights, lower temperatures close the vein from going into the leaf and prevents these sugars from moving out. This causes the red, purple and crimson tint on the leaves.

However, as the weather starts to move into its winter temperatures, fall foliage and colors on the leaves can be lost. According to the U.S. Forest Service, perennial plants, including trees, must have some sort of protection to survive the freezing temperatures and other harsh winter conditions. Stems, twigs and buds are equipped to survive extreme cold so that they can reawaken when spring heralds the start of another growing season.

Unlike other parts of the plant, tender leaf tissues freeze in the winter. This causes plants to either toughen up and protect its leaves or dispose of them, why so many leaves end up falling to the ground when the winter season begins.

When the leaf tissues start to freeze in response to shortening days and declining intensity of sunlight, the veins that carry fluids into and out of the leaf gradually close off as a layer of cells form at the base of each leaf. These clogged veins trap sugars in the leaf and produces anthocyanin, a chemical that plays a protective role in plants against extreme temperatures. Once this separation layer is complete and connecting tissues are sealed off, the leaf is ready to fall.

For more information on winter’s impact on fall foliage around Virginia, visit U.S. Department of Agriculture’s website.