Fall is such an appropriate name for the season — leaves are falling with or without changing color! And it seems to be getting an early start this year, as many landscape plants have started their annual ritual of changing colors and dropping leaves.
Certainly, some of the reason why plants display fall colors has to do with the genetic makeup of the plant. That doesn’t change from year to year. But the timing and intensity of fall colors do vary, depending on factors such as availability of soil moisture and plant nutrients, as well as environmental signals such as temperature, sunlight and length of day.
Landscape plants often begin their fall coloration and leaf drop early when under stress, and we’re more used to stress being from hot, dry summers. While this didn’t seem like a particularly stressful summer for most areas, I suspect that the unseasonably cool temperatures, perhaps coupled with unusually heavy rains, have triggered this year’s early change.
Maples, sumac and burning bush are among the plants that I have noticed turning especially early. Some plants, such as river birch and crabapple, may be dropping leaves a bit early, but it could be due to other stress-related issues.
White pine is also showing a dramatic early shedding of older needles, about a month ahead of last year. Although evergreens provide green color all year long, their individual needles do not live forever. Evergreens shed their older (inner) needles to make room for new growth, with different species varying in life span. Some species of evergreens have a more noticeable leaf drop than others. White pine is usually most dramatic, sometimes accompanied by arborvitae. When they drop their old needles all at once, it can be quite alarming if you don’t realize that it’s perfectly normal.
On other species, needle drop occurs gradually, with a small number of needles falling at one time. The older needles of yew shrubs will turn yellow and drop in late spring or early summer. Broad-leaved evergreens, such as rhododendrons, drop their 2- to 3-year-old leaves in late summer and early fall.
Inner and lower needles that are more shaded from light are usually the first to drop. Pruning excess growth and dead limbs can help open the plant to more light. But, for most plants, there’s no need to worry; they are just doing what comes naturally.