is nearly equal. The word equinox means “equal night”. As the weeks march on, the earth tilts on its axis and the Northern Hemisphere is farther from the sun, decreasing the amount of time the sun is over the horizon, changing our weather patterns and creating distinct seasons.
and Horse Festival. The festival takes place on September 29th and features a plant sale, equine demonstrations, a harvest market of locally grown and produced items, horticultural talks, a six-acre corn maze and children’s activities, including a tree scavenger hunt. The majestic trees around the garden grounds are the focus of the activity. This time of year, I am often asked, “What will the colors be like this fall?” referring to the changing leaves.
So where do these colors come from? The green pigment
chlorophyll is abundant in the leaves throughout the summer as it carries on the job of absorbing the energy from sunlight needed for photosynthesis. Photosynthesis uses carbon dioxide, water and sunlight to make sugars necessary for a plant’s survival. Chemical changes take place to prepare a tree for winter, triggered by change in day length and temperature.
from year to year since the compound carotenoid is always present in the leaves of birch, locust, and poplar, to name a few. Red and purple hued leaves are more brilliant when warm sunny days produce sugars which are then trapped in
the leaf when the night cools, causing the formation of red pigments called anthocyanins. Varying amounts of chlorophyll residue and pigments produce the different shades.
Each tree species displays a dominant autumn color that is more or less intense based on environmental factors. Degree and duration of
fall color depends on temperature, light, and water supply over the entire growing season. The checklist below offers some clues to determine the
potential brilliance of fall foliage.
Summer not too hot; limits stress
Summer not too dry; limits stress
Warm sunny fall days to produce sugars
Cool fall nights, not freezing
Warm, wet fall lowers intensity of colors
Severe frost browns the leaves, early drop
Cloudy fall days
Early onset of cold weather – the leaves may not drop
Autumn is a time of transition from an actively growing tree
to the dormancy of winter. All parts of a broadleaf tree except the leaves can
endure winter temperatures. A leaf releases from the branch when a corky layer is formed at the base of the leaf stalk, thus sealing the twig from water loss. Sugars stored in the branches, trunk, and roots sustain the tree until it awakens in spring. Buds form in the fall and lie dormant until after the spring equinox when lengthening days and warmer temperatures bring the promise of renewed life to the winter landscape. It seems that because autumn colors are fleeting, it adds to their appeal. We have had conditions from both the “positive” and “negative” checklist, so maybe this year will be just right.
Curator of Landscape