Ever wonder why some years your prized Japanese maple trumpets color in autumn, while in other years it seems less enthusiastic? There's a good reason. Like our moods, the color intensity of fall foliage changes with the weather.
The changing color of fall foliage is a simple chemistry lesson. Chlorophyll is what makes leaves green (and enables plants to use sunlight to create their own food). As days become shorter and temperatures drop, chlorophyll production slows to a stop and the other pigments in the leaves get a chance to show themselves.
The two primary pigments are carotenoids that produce orange, yellow, and brown colors, and anthocyanins that are responsible for resplendent reds. The orange pigments (carotenoids) are present in leaves year round and get to shine when the green chlorophyll takes a break. Because the orange pigments are constant, their showiness in the fall is predictable. But, the red pigments (anthocyanins) are created in the autumn in response to light, plant chemical changes, temperature, and water supply. This is where weather affects the brilliance of the fall color display.
Above: Photograph by Rob Weibe.
Warm days and low temperatures (above freezing) at night boost the production of the red pigments, producing a more dazzling display. But early frosts weaken the colors. What weather makes for the best fall foliage show? According the the US Forest Service, "a succession of warm, sunny days and cool, crisp but not freezing nights seems to bring out the most spectacular color displays."
Moisture also plays a role. "A late spring, or a severe summer drought, can delay the onset of fall color. A warm wet spring, favorable summer weather, and warm sunny fall days with cool nights should produce the most brilliant autumn colors." Bring out the crystal ball (or at least the Farmer's Almanac).
Here are a few of our favorite performers in the fall foliage show:
Above: The quintessential fall leaf is that of the sugar maple, prominent in the Northeast of the US. Photograph by Liz West via Flickr.
Above: Even in San Francisco, fall is starting to show its colors on a Japanese maple in my backyard. Looking for a dramatic fall show stopper? Japanese Maples are a sure bet. Photograph by Janet Hall.
Above: Yellow oak trees are a consistent fall performer in yellows and golds. Photograph via Christmas Notebook.
Above: The fan-shaped leaves of the ginko tree put on a fall show in yellow. Photograph by Pinehurst via Flickr.
Above: The sassafras tree is not only aromatic but also a brilliance of orange in the fall. Photograph via Get Your Botany On.
Above: After producing summer fruits, the unsuspecting blueberry bush offers a show of red leaves. Grow Organic offers a selection of Blueberry Bushes suitable for many climates. Photograph via Away to Garden.
Above: The Purple Smoke Bush is prized for its year-round color show. Red in spring, purple in summer, turning to orange in the fall, it is available at Wayside Gardens for $22.95. Photograph via Moosey's Country Garden.
Above: Favored for its red stems, the leaves of the Red Twig Dogwood turn a brilliant red or red-purple in the fall. Photograph via Nami-Nami.
Above: Red Twig Dogwood's namesake: the red twigs that add color to the garden after the leaves have dropped for the winter. For the reddest of stems, consider the Arctic Fire Dogwood available for $14.95 through Bluestone Perennials. Photograph via the University of Maryland Arboretum and Botanical Garden.
Fall's here! See our earlier feature to Identify Those Colorful Leaves.
- Nature & Environment
- Natural Phenomena
- fall foliage