While boating over Labor Day weekend, my daughter reported seeing a maple tree in Freeport with nothing but bright red leaves. Surely it was way too early for trees to be changing into their autumn garb. Maybe not …
One great reason to live in New England is the stunning fall foliage. Unseasonably warm weather with the full palette of colors should tide you over until January, when you dream of an escape to sunnier, warmer climes. Autumn colors are big business, as the surge of leaf peepers extends tourist season beyond Labor Day well into October, yielding a final hurrah of tourist dollars to keep the home fires burning through next year’s mud season.
We all have our theories as to when and why the leaves change and drop. It turns out that most of our theories are wrong, and scientists freely admit they do not fully understand the phenomenon of leaves changing colors. Hang in there through some biology to learn what is going on.
Plants have an amazing ability to process water and carbon dioxide in a process known as photosynthesis. The energy source is sunlight, and the outputs are simple sugars to nourish the plants and oxygen for us to breathe. The magic takes place thanks to a green pigment in leaves known as chlorophyll. As the growing season progresses, chlorophyll breaks down, but with enough sunlight, the plants replace the chlorophyll and the leaves remain bright green.
We all learned that there are two families of trees: the conifers, such as spruce and pine; and deciduous trees, such as maples and oaks. All of them use photosynthesis, with one big difference. While deciduous trees only have leaves from spring through early autumn, most conifers retain their leaves (more commonly called needles) all year long. The conifers have evolved to use photosynthesis throughout the winter months, with a waxy coating on their needles that minimizes water loss.
Thanks to the Earth’s tilt along its north-south axis, and its ongoing revolution around the sun, we experience an annual change of seasons. Every six months the hours of daylight wax and wane, with an impact on all living things, including plants. As summer winds down, cooler nights and shorter days cause plants to stop making new chlorophyll because the energy required is higher than the yield of simple sugars.
As the chlorophyll gradually disappears, yellow and orange pigments called carotenoids, already present in the leaves, become visible to us. Carotenoids are found in many living things and are responsible for the bright colors you see in corn, bananas, carrots and egg yolks. As the leaves continue to decline, the yellow and orange pigments yield the colors you see on hickory, ash, maple, aspen and birch trees.
What about the glorious reds of autumn? Thank other pigments known as anthocyanins, produced in late-summer leaves. Anthocyanins yield the bright reds and purples of the maples, oaks and dogwoods, while combining with carotenoids for fiery reds, deep oranges and bronzes in some hardwoods.
The more sun during late summer and early fall, the more anthocyanins produced and the brighter the autumn leaves. Because New England has a very high percentage of tree species producing anthocyanins (roughly 70%), our fall foliage is nearly unrivaled anywhere on Earth.
Autumn finds the trees gradually shifting from growth and energy production to the retention of nutrients in anticipation of the harsh winter months. Environmental changes taking place around the trees trigger the loss of their leaves. This occurs because trees create a physical barrier between the branch and leaf, protecting the branch but starving the leaf of water and nutrients. Those falling leaves still play a valuable role by serving as mulch to protect tree roots through cold winters and breaking down into nutrients for future growth.
Annually there is a debate as to when foliage will “peak,” with newscasters displaying elaborate maps to pinpoint the best colors. Data shows that global warming and rising carbon dioxide levels have delayed foliage season by four weeks since the 19th century. Bigger storms and variable weather patterns further complicate predictions.
The website mainefoliage.com will help to plan your leaf-peeping journeys. In late September, head to Moosehead Lake, then try Grafton Notch State Park in early October. In middle October, zip up to Fryeburg, then back to Harpswell, and perhaps Wells in late October. If you still need more foliage, head to New Zealand or Argentina during mud season!
