It's time to stop taking Maine's beautiful birches for granted.
The synergy between birch trees and Maine goes well beyond practicality. Maine artists, including the late Neil Welliver (think of his 1984 serigraph Birches), have enjoyed capturing this hardwood's elegant silhouette and sumptuous coloring (birch foliage provides the yellow highlights in the autumn landscape). For similar reasons, gardeners from Boothbay to Bethel consider birches, especially the paper birch, indispensable. The tree's richly textured bark, in hues from reddish brown (young specimens) to snowy white (mature trees), makes it a focal point even in winter (which it takes in stride, even in temperatures as low as sixty-five degrees below zero Fahrenheit). Sited thoughtfully, birches can link a house to the woods just beyond. "The white trunks look close, even though they may be far away," notes South Thomaston garden designer Lee Schneller. "If you plant a few in the foreground, others in mid-ground, and still more in the background, you'll knit together an entire landscape. Birches do a huge job."
Lately, though, Maine's native paper birch and yellow birch (Betula alleghaniensis, with bark more bronze than white) have been eliciting concern as well as admiration. The crowns of many specimens prominent in domestic settings have thinned and died, while entire stands in forests and along rivers often have no tops at all. "The '98 ice storm took a heavy toll on the birches," observes arborist Tooley, who founded Northeast Tree Service, with headquarters in Camden, in 1971. "But that's not the only problem. Just like sugar maples, birches are very susceptible to pollution and acid rain. And the drought in 2000 made everything worse."
Tooley regularly counsels homeowners distraught over the impending death of a beloved birch that may have stood sentry for generations in the front yard or at the family camp. "Even if an ice storm or pollution or drought doesn't kill the tree outright, the bronze birch borer often will," he says. About the length of a thumbnail, these opportunistic, iridescent pests seek out trees in distress. Rarely seen, the borers start at the top of the tree and eat their way down. By the time dieback at the tree's crown is noticed, little can be done to save the tree. Aiding and abetting the borers are leaf miners, which cut round holes in foliage and turn it brown. Damage done by leaf miners usually isn't fatal, but it adds to the stress that compromises birch health.
While it's difficult not to feel helpless in the face of industrial pollution and Mother Nature, there are steps home-owners and gardeners can take to reduce the death toll. For one thing, "You can watch the stock you buy," Tooley counsels. "Look for a bulge on the bark, a sign that borer larvae have been feeding underneath." You might also see small holes where they've made their exit. For compromised trees already in the landscape, "Consider applying liquid or granular fertilizer - 5-10-5 is good - in early spring, right after the ground thaws. But don't overdo it."
Urban and community forester tish carr (who, like the poet e.e. cummings, shuns capital letters in her name), says that birch trees fare best in settings with little or no traffic. "If you decide to build a house or a garage near a birch tree, remember, all it takes is one pass with a truck or back hoe to compress the tree's root system. Quite possibly, you'll have killed the tree." Even heavy foot traffic can cause root compaction. If a well-traveled path or driveway predates a nearby birch, the tree's roots will accommodate it. But if the path is created near an established tree, the birch can suffocate. "This, in addition to the pollution problem, is why birches make lousy street trees," she adds.
Carr says poor pruning is another, often fatal, mistake. "Birches are bleeders," she notes. "If you cut them in spring, when the sap is running, you'll end up with an oozing sore. It's best to wait until July or later." When you do prune, avoid cutting flush with the trunk, as you may injure the branch collar and allow insects and disease to enter. Cuts made too far from the collar can impede healing, as well. Finding the sweet spot may take help from an arborist or a little homework (see the U.S. Forest Service's pruning handbook on the Web). Carr, who with Dale Gilmour operates Skyline Tree Care and Forestry Services, in Belgrade, counsels her lakefront clients to take one other precaution. "Where beavers are a problem, waterfront birches should be wrapped with wire netting from their base to about one foot up the trunk. Beavers love birches."
At the Pine Tree State Arboretum, on Hospital Street in Augusta, Executive Director Stephen Oliveri tells visitors that planting the right species can make a difference if you want your birch to last at least as long as you do. "Native trees are simply hardier," he notes. In his opinion, river birch (Betula nigra, with dramatic, shaggy bark), doesn't have the longevity of Maine's native species, which include gray birch (Betula populifolia) in addition to paper birch and yellow birch. Indigenous from Massachusetts to Florida, river birch withstands hot summers reasonably well (and resists borers, too) but isn't as cold tolerant as its native cousins. Still less reliable is European white birch (Betula pendula), especially the weeping forms, perhaps the most susceptible to borers of all the birches.
For those who perceive a species in decline, Charlene Donahue, forest entomologist for the state of Maine, offers some comfort. "Birches are not long-lived trees," she notes. "Seventy years is about all you can expect. Many of the large birches you see around houses were planted during the development boom that followed the Second World War. These trees have simply reached the end of their natural life span."
For their part, though, when the subject is birch, Maine's gardeners and artists, as well as the state's avid hikers and kayakers, are in agreement: It's time to stop taking these breathtakingly beautiful trees for granted.
" Plant birch trees in full sun in acidic soil (a pH from 5 to 6.9 is optimal); do not amend the soil. In a hole five times the diameter of the root ball, spread out the roots to prevent girdling, which can choke off sap flow and water uptake.
" Water new trees every week and established ones during drought. Don't overdo it, though, as birches are sensitive to changes in the water table.
" Prune to remove dead matter only. Cutting into living tissue in an attempt to artificially shape the tree is comparable to amputating a human limb.
" Growth rate for healthy birches is fairly rapid, averaging eighteen inches a year.
- By: Rebecca Sawyer-Fay