As the languorous days of summer ebb, autumn hastens in with an upbeat, quickened tempo while the cooler temperatures inspire more activity. The verdant hues of summer give way to jazzier tones of crimson, gold, fiery orange, and maroon. The cause of this magnificent display of color is a fascinating, complex biochemical process. In the fall, daylight length and intensity decrease and air temperature drops as cooler air blows in from the north. Because cooler air is drier, many trees and shrubs shed their leaves to preserve moisture and prevent drying out. These are called "deciduous," from the Latin deciduus meaning to fall off; thus the “falling off season,” or, as we say, fall.
During this shedding process, the foliage color changes as chlorophyll, the green-colored pigment in leaves, begins to disintegrate. As the chlorophyll breaks down, other pigments present in the leaves are displayed and the show-stopping colors of autumn are revealed. The more stable yellow and orange pigments found in all green plants known as carotene and xanthophyll (the very same pigments found in carrots and bananas) remain, and "turn" the leaves yellow, gold, and orange. Birches (Betula sp) provide clear yellows while beeches (Fagus sp) produce bronzy yellows in our local landscape.
Some trees and shrubs produce more glucose (sugar) converting it to another pigment, anthocyanin, to produce the red, scarlet, and purple colors. Bright, clear fall days combined with cooler night temperatures produce more red pigment. A number of our native trees show the red color to great effect: maples (Acer sp) yield the signature flaming reds of the New England landscape, while other natives such as dogwoods (Cornus florida), sumacs (Rhus sp), tupelo or sourgum (Nyssa sylvatica), and sourwood (Oxydendron arboretum) present us with their particular glowing reds. Oaks (Quercus sp), which have a high level of tannin, frequently just turn brown as the chlorophyll disappears, but in some years can provide spectacularly rich and glowing colors. There are many varieties of oak trees, but the red oak group provides the best fall color, particularly the scarlet oak (Quercus coccinea) with a range from maroon to a deep claret red.
Color in nature serves dual purposes; in flowers, to attract pollinators and in fruits to attract birds or mammals for seed dispersal. But according to scientists, the autumnal metabolic changes are still a mystery with no obvious biological or botanical purpose, and the brilliant seasonal colorations of our regional landscape are not readily found elsewhere in the world. Sometimes it is best just to accept the mysteries of nature and enjoy the magnificent display of fall in all its glory.
FALL CHORES IN STORE
- Plant seeds of leaf lettuce or other greens for a quick crop.
- Continue deadheading annuals or replace them with seasonal choices.
- Cut back any perennials with brown foliage.
- Mow lawn to a height of two to three inches.
- Order spring bulbs.
- Fertilize the lawn, renovate bare patches, or seed a new lawn.
- Dig up summer bulbs like dahlias and store them in peat moss.
- Divide perennials and cut them back, but leave some so wildlife can nibble on the seedheads.
- Grab your rake rather than the mower. Rake up fallen leaves and shred them to use as a winter mulch or add to the compost pile.
- Plant spring bulbs before the ground freezes.
- Top up mulch in ornamental beds.
- Plant a cover crop in the vegetable patch to prevent nutrient loss and reduce erosion from wind and water.