Spectacular autumn color is so New England that we tend to take it for granted. However, there’s nothing like it elsewhere. This annual show, starting in September in Maine and arriving in Connecticut around late October, is the product of our advantageous geographical location and our magnificent native hardwood trees.
Why are we unique? The geographical and climatic conditions essential to great fall color converge in only four places: northeastern North America, southern-most South America, southwestern Europe, and eastern Asia. These four places are all located in temperate regions. Temperate regions experience sharply contrasting summer and winter seasons and have trees that have co-evolved to abruptly shed their leaves at summer’s end. These four places also have the right climate. While the details get complicated, vibrant autumn color is created by a warm, wet spring, favorable summer weather that’s not too dry or too hot, and seasonably warm, clear, fall days with crisp, but not freezing, nights. In all four cases, proximity to a sea coast moderates the weather, making these conditions most likely.
The New England trade secret that makes it a tourist magnet is having the right trees turning in unison with the right mix of colors. Artists know that brilliant color is the result of the interaction between colors, particularly colors that are opposite on the color wheel. Thus, deep purples and burgundies make the yellows glow, lingering greens put fire in the reds, blue skies spark the oranges, and a few fluffy white clouds add even more sparkle. What makes New England unique is that we not only have the location and the climate, we have the trees. The crown jewels, some say, are our native maples.
The science of it
On a cloudy fall day, when a sugar maple glows so brightly that it seems internally lit, it’s hard to credit the affect to the chemistry of leaf cells, but so it is. Summer leaves appear green due chlorophyll—that magic substance that plants use to transform sunlight, air, water and soil into food and shelter for all living things while filtering pollutants and moderating temperatures. Chlorophyll is unstable, so leaves are constantly synthesizing it with the aid of summer’s warmth and sun.
Under the chlorophyll, botanists say, lurks carotene, the pigment that turns corn yellow and carrots orange. Leaves often start yellowish in the spring before the chlorophyll develops. Leaves with high carotene levels look brighter green or yellow-green in summer. Carotene is a stable substance that lasts longer than chlorophyll and tends to be constant from year to year.
As short days, low light intensity, and cool temperatures signal trees to close off the leaf veins in preparation for dropping the leaves, chlorophyll production wanes and carotene shines through. Overly warm, bright fall weather can delay or dull fall color because the leaves are still making summer levels of chlorophyll. Under the carotenes are the bitter-flavored tannins, the browns that remain last of all. Many trees turn yellow or ochre, and then brown—pretty when mixed with evergreens, but not a world-class show.
So where do our amazing colors come from? Anthocyanins are tricky, finicky red and purple pigments that help impart flavor to grapes and color to autumn leaves. Anthocyanins turn strawberries red, grapes purple, and blueberries blue. Anthocyanins give temporary color to some spring leaves before the chlorophyll kicks in and remain all season in the leaves of red-leafed trees. In the fall, for reasons not fully understood, leaves with high sugar content use the lingering sugars to create anthocyanins.
As wine lovers are only too aware, sugar and, hence anthocyanin, production varies significantly from year to year, place to place, and plant to plant. The PH affects it—more acid becomes more red; less acid becomes more purple. The moisture affects it: not enough water and the leaves die; too much water and the sugar is too diluted. The light affects it—too much light and the leaves are still making chlorophyll, not enough light (too many cloudy, rainy days) and the reaction that creates anthocyanins can’t take place. Temperature affects it. Cool nights kept the leaves from draining out sugar, but freezing will kill the leaves; too cool in the day and the anthocyanin can’t get made. The plant’s health and nutrition affect it. Stressed and dying trees, and overly-fertilized trees, can turn earlier or later, often with more intense color. The tree’s specific heritage affects it. Cross-breeding and in-breeding result in trees that vary from their species’ norm.
In a good year, anthocyanin, mixed with carotene and tannin, transforms the autumn yellows and browns into brilliant reds, fiery crimsons, deep oranges, golds, bronzes, burgundies and purples. While anthocyanin production is iffy, New England gets the edge due to the high concentration of sugar in the leaves of our sugar and red maples.
The trees: introducing our maples
THE NATIVES: The branches of maples tree are opposite each other rather than alternating on the limb. Opposite arrangement is rare among native trees, so it’s easy to spot maples. The only other common native opposite-branched trees in our area are ashes, compound-leaf trees often confused with hickories, which turn yellow and ochre.
SUGAR MAPLES: The first maples to signal the arrival of autumn are our stately sugar maples (Acer saccharum), which are without question, world-class tree champions. The autumn color ranges from brilliant red, burgundy and orange to yellow and lime; leaves will often turn from the leaf tip in beautifully graduated shades. The classic sugar maple leaf, reproduced on Canada’s flag, has five triangular lobes with deep U-shaped indentations between the lobes; the leaf edge is smooth and wavy.
Sugar maples, famous for their sap, are also prized their outstanding hardwood lumber, which provides flooring for the NBA and birdseye maple for fine furniture. The wildlife also appreciates sugar maples. Songbirds nest in the leafy crowns; birds and small mammals eat the seeds. Squirrels tap the sweet sap. Insects take small bites here and there and then, in turn, become bird food.
The sugars are among our most beautiful trees. Semi-symmetrical with rounded crowns, straight trunks and gracefully curving branches, sugars can grow over 100 feet and live 300 to 400 years. The major lower limbs often curve upward at the base, like a candelabra. The smooth gray trunk bark splits vertically with age into long curving furrows with cinnamon undertones, further enhancing the tree’s beauty.
Sugars are at home in our mixed-hardwood forest, along with beeches, oaks, hickories, and birches. While evolved as forest denizens, sugar maples make impressive specimen trees, shading yards, parks, town squares and meadows. Sugars, for all their glory, unfortunately, don’t cope well with acid rain and other air pollutants, urban road salt, yard pollutants or flooding. Further, sugars don’t like foot traffic or equipment compacting the soil over their roots. Also, our northern sugar maples are not heat-hardy and, under present climatic conditions, aren’t found south of Georgia and the Carolinas (about Zone 8A).
According to the National Wildlife Foundation, we would go a long way toward stopping global warming if we each planted an additional tree to absorb the excess CO2. Among those trees, we should be encouraging are young sugar maples. Sugars should be planted away from road salts, car exhausts, foot traffic, and mowers.
RED MAPLES: Next to turn after the sugar maples, and almost as important to the New England autumn pallet, are our staunch, adaptable red maples (Acer rubrum), also known as the swamp maple, one of North America’s most wide-spread native hardwoods.
Red maples, confusingly, do not have red summer leaves. (In the maple clan, red summer leaves are limited to certain Japanese maples and to certain cultivars of the Norway maples.) However, the autumn color range of the red maples is even greater than the sugars —every shade of red, orange, yellow, and lime, sometimes mixed with an almost purple. The leaves can be a single color or lovely calicos. The best way to identify the red maple leaves: the three prominent leaf lobes point forward, instead of radiating outward, and the indentation between the leaves is V-notched, not rounded. Further, the leaf edge not smooth but toothed (serrated). The red maples tend to be shorter than the sugars (up to 80 feet), and shorter lived (up to 150 years). Like most maples, the young tree’s bark is gray and smooth. Red maple bark becomes shaggy and craggy with age.
When not lighting up the fall sky, red maples are equally valuable as street shade trees and as the guardians of our fresh-water wetlands. The ability of the red maples to tolerate the damp, low-oxygen zones under swamps allows the trees to handle the similar conditions under urban sidewalks. Their cultural versatility, wonderful fall color, and urban-hardiness have resulted in them being almost over-planted in some areas. (Reds are urban-hardy but not made out of steel, so they aren’t the best choice for the middle of an oven-hot parking lot, for example.)
Red maples are tapped commercially for sugar but have a short, early season as the sap flavor changes as the buds break in early spring. One of note of caution: while red maples are a prime source of food and habitat for riparian wildlife, red maples are poisonous to some mammals. Accordingly, red maple leaves should not be included indoor fall bouquets, and most maples shouldn’t be planted near horses.
SILVER MAPLES: Our third major native maple is the towering silver maple (Acer saccharinum), the lacy-leafed cousin of the red maple. Silvers’ red pom-pom flowers are the first in spring, sustaining many early-waking pollinators. Silvers can have multiple trunks reaching up into fountain-like shapes. The trunks become massive and gnarled, and the silver-gray bark extremely shaggy with a notable orange undercoat. Silvers have giant, golden seeds that are important late spring food for young mammals and many birds, including our reviving turkey population. Silvers are prefect trees for large open spaces and along the water but suffer from limb-drop, particularly in high winds, so aren’t the best tree for a small yard or close to structures.
For all their good points, silvers don’t have much in the way of fall color. The leaves tend to drop before turning or go straight to brown, with just a brief pass at yellow. Silvers growing on the water’s edge, though, seem to hold a bit of buttery yellow, and even an orangey-red, long enough to appreciate. The five-lobed leaves are so deeply cut that they can’t be confused with the leaves of any of our other local maples.
BOX ELDERS: Lastly, there are the box elders (Acer negundo), which are expanding their native range north and east into New England. The “ash-leaf” maple has beautiful winter buds, summer leaves and year-round stem color, but alas, it’s a dud in the fall: greens go dirty yellow, then brown. Box elders are weedy, so they are likely to plant themselves, particularly along the coast.
THE FOREIGNERS: It is impossible to consider New England maples without mentioning the foreign maples that have made New England home. It’s no mistake that the foreign-invader maples keep their leaves longer than the natives; the foreigners evolved in different environs and part of their ability to out-compete our natives is their longer growing season.
The petite, lacy Japanese maples (Acer palmatum, etc.) grace many an urban yard with jewel-like mid- to late-season color. Japanese maple leaves take many forms and colors but are generally smaller and more ornate than those of other maples. In Connecticut, with current temperatures, Japanese maples are “nice small trees” good for urban yards and under electric lines. They grow slowly and behave themselves. Further south, however, these Asian maples are invasive, imperiling the forest understory.
The ubiquitous Norway maples (Acer plantanoides) turn late and often hold their leaves the longest, often being the only tree still in color at the tail-end of the season. Norways usually turn a buttery lemon yellow but can be orange, red or a combination. Once prized as shade trees, Norway maples are now banned from sale in Connecticut due to the trees’ environmental destructiveness. The Norways’ thick surface roots, dense shade and mushy fallen leaves can kill everything beneath them in lawns and the forest understory. While Norways can no longer be sold, each existing tree annually produces thousands of winged seeds that are wind-carried for miles and have a sprouting rate around 90%. They are particularly a threat to our hardwoods, such as sugar maples, and to our woodland wild flowers.
We have two other fast-spreading alien maples: the sycamore maples (Acer pseudoplatanus) which lack fall color, and the amur maples (Acer ginnala) that turn red fading to yellow. These menaces-to-be are both classified by the State as potentially invasive.
So, which region is the best?
In colonial days, Europeans didn’t believe reports coming back from New England and accused landscape painters (photo-journalists of their days) with grossly exaggerating New England’s fall color. It was, certainly, too good to be true, compared to the color seen in most of Europe.
Today, everyone who conceivably can is touting the comparative autumn magnificence of their locale, often to the tourist trade. Regional pride is a good thing, I guess. But come this October, walk out your door, turn toward the closest sugar maple, and try to imagine another tree that’s its equal.
