Have you noticed many plants already starting to turn fall colors? Rhonda Ferree, Horticulture Educator with University of Illinois Extension, says that it is still a bit early for most fall coloring. Ferree suspects that early fall color is often a sign that a plant is under stress.
"Stress is defined as exposure to unfavorable conditions. One sign of plant stress we see this time of year is early fall coloration". The many plants currently exhibiting early fall coloration include burning bush, river birch, crabapple, flowering dogwoods, ornamental pear, and many maples.
Normal fall coloration and leaf drop is primarily triggered by shorter days and lower temperatures. So how do leaves change colors? Ferree says that it is very complicated. "With cooler, shorter days the leaves stop producing chlorophyll, which is responsible for the green color of leaves in the summer". "As the plant produces less chlorophyll, the other color pigments within the leaves begin to show".
Warm, sunny days and cool nights help increase the color intensity. This must happen gradually. As the leaves stop producing chlorophyll, the coloring chemicals build up inside. A warm, sunny day causes more intense colors and the cool, long nights help shut down the leaves' food production.
However, Ferree explains that other factors can also lead to leaf coloration. "This summer's drought severely stressed many plants". "With shorter days, some plants under stress will start coloring early". Although early fall coloration is an "alarm" response to stress, it does not necessarily represent a threat to plant life. "Determine the source of plant stress". By far, the majority of plants showing early coloration are undergoing drought stress. This is especially true of new plantings and typically is a result of the roots' failing to supply sufficient water to the leaves.
Ferree recommends watering plants that are stressed to encourage recovery growth and root revival. "Apply enough water to penetrate deeply within the drip line. Never overwater". To prevent plants from sending out succulent, frost-susceptible growth, avoid fertilizing or pruning until the plants are dormant. The added water will not reverse the early coloration, but it will better prepare the plant for winter and possibly less future decline.
So will this summer's drought affect our fall color displays in 2012? Ferree expects that the drought will result in a shorter, less intense fall color season. "Many plant leaves have already turned brown or have brown edges as a result of the drought. Those leaves will not turn their usual red, yellow, and orange fall colors." Still, Ferree has a glimmer of hope. "Our recent rains might revive trees enough to allow better fall coloring."
Source: Rhonda J. Ferree, Extension Educator, Horticulture & State Master Naturalist Coordinator, firstname.lastname@example.org
Pull date: October 1, 2012