Jack Frost sometimes gets credit for the beautiful hues, but in reality, fall color is controlled by the plants’ genetic and environmental factors.
Carotene and xanthophyll are yellow pigments produced in foliage all year, along with chlorophyll, the green pigment. In autumn, when short days and cool night temperatures slow down the production of chlorophyll, it eventually disappears. Then the yellow pigments that have been masked by the green chlorophyll begin to show up.
Some plants produce anthocyanins (red and purple pigments), which increase with the sunny days and cool nights as more sugar enters the leaf. This produces the brilliant red leaves.
The tan and brown leaves of the oaks are caused by the increase of tannis, which accumulates as the chlorophyll fades.
Fall color begins in the middle of September and continues until the first freezing temperatures stop the coloration process and blacken the leaves.
Since I’ve explained how the trees and shrubs come to display their colors, I would like to suggest some plants that will offer the optimum fall beauty we all desire.
Small trees (10-25 feet), full sun: amur, paperbark and tartarian maples and serviceberry. Partial shade: Japanese maple, American hornbeam and Chinese sumac.
Larger trees: ginko, sweet gum, white oak, river birch, sugar maple (autumn flame, red sunset) and October glory.
Shrubs for autumn foliage in Zone 5: viburnum (cardinal candy), 5-6 feet, red berries; viburnum (Juddi) 6-8 feet, bright red; viburnum (Koreanspice) 5 feet, reddish, purple; beauty bush, 4 feet, purple berries; clethra, 3-8 feet, deep yellow to orange foliage; red twig dogwood, 9 feet, red, need to prune every two years, has winter color, too; pyrancantha, scarlet orange.
Shrubs for color and wildlife: viburnum (leatherleaf) 8-10 feet, blue-black berries; American elder, 12 feet, blue-black berries; bayberry, 8-9 feet, need male and female for berries; winterberry holly, 10 feet, bright red berries, witch hazel, 15 feet, bright yellow; and Cytisus, yellow flowers with crimson wings, branches stay green all winter.
“Listen the wind is rising, and the air is wild with leaves.
We’ve had our summer evenings, now for October eves!”
– Humbert Wolfe