| Adrian Higgins |
WASHINGTON (The Washington Post) – A number of conifers are candidates for the Official Evergreen of Winter, but among the leaf-shedding shade trees there is just one superstar, the birch tree with its peeling snow-white bark.
Birches grow in groves as nature’s marble columns. Against a clear blue sky, they seem to capture the crisp, cold intensity of the season. At night under the moon, they glow like a company of ghosts.
If you have moved to a southern climate from northern regions, you will find yourself missing birches, or at least the white-barked versions. They dislike the heat and the humidity of hotter summers, they get stressed, and they are attacked by a deadly pest named the bronze birch borer.
You can get used to a new treescape and grow to like its familiarity. But for once-boreal creatures such as myself, the absence of the white birch is always felt and especially in winter.
In North America, the white-barked beauty is the paper birch, Betula papyrifera. This is the tree whose bark can be cut away in generous sheets. This is handy for building birch canoes, but not so great for the donor tree. Donald Culross Peattie, in his book A Natural History of North American Trees, speaks of the first experience of paddling a light, strong, birch-skinned canoe. “At the first stroke of the paddle it shot out over the lake water like a bird . . . for on all the waters of the world there floats no sweeter craft than this.”
I prefer my white birches in situ, and think of their considered placement on a hillside at the estate named Naumkeag in the Berkshires in Stockbridge, Mass. Here, the landscape architect Fletcher Steele (1885-1971) alluded to Italian villa stairs and fountain grottoes with the fluid tracery of steel-tubed railings, pairing this abstraction with a grove of multi-trunked paper birches. The resulting Blue Steps, dating to 1938, are an ingenious synthesis of ancient and modern, Old World and New.
As the trees died over the years, the birches were replanted until few of the originals remained. In 2013, as part of a three-year restoration of the estate’s gardens, all the old birches were removed and fresh ones planted, some 60 trees. Archival photos aided in adhering to Steele’s original design. All have now matured and “there’s white bark growing through all of them,” said Mark Wilson, curator of collections for the Trustees of Reservations, the state preservation group that runs Naumkeag. The property is open from April to October.
The white birch of Europe is the silver birch, Betula pendula, named for the way its branches hang down. You will find self-seeded thickets of it from Bavaria to Scotland and beyond. There is something serene and timeless about such places, even though the birch is a relatively short-lived tree.
An Asian species, found in Tibet and southwestern China, named Betula szechuanica, is thought to be the whitest of birches, according to the newly published book Birch by Anna Lewington. Within the book’s pages, a variety of another species named the whitebarked Himalayan birch looks as if it has been formed of alabaster. But I am taunting you, for to grow them in a hot, humid climate is to invite disaster. As the tree guru Michael Dirr writes of planting the silver birch in such a setting, “you might as well send a formal dinner invitation to the bronze birch borer.”
If you live high in the Appalachians or in northern latitudes, you could turn to a few native species of birch, the grey birch, the sweet birch and the yellow birch. They have interesting bark – the yellow birch has a cherrylike bronze coloration and attractive peeling – but none approaches the chalky beauty of the silver or paperbark birch.
There is one birch for the South, namely the river birch, whose thick, dark-grey trunks can be found along stream banks, leaning into the bright open water.
Varieties of this species make for handsome garden plants; the best-known is Heritage, others are Dura-Heat and City Slicker.
They have lovely peeling bark and can display a pleasing salmon-tan coloration. But there are drawbacks. The strong colour of youth dulls with each passing year, and the trees develop into large specimens, far greedier for space than most gardeners anticipate.
They also don’t like drought stress and will drop leaves when unhappy. Another problem, for me, is that Heritage (also known as Cully) was simply overplanted over the past 30 years. We had too much of a good thing. Or perhaps the real problem was that it wasn’t bone white.
Why are birches white, you ask, when most trees make do with brown or grey?
One theory is that as a thin-skinned northern species, the birch is prone to the phenomenon of winter splitting. The low sun heats the night-frozen bark too quickly and it splits. Birches figured out that white pigmentation reflects the rays and reduces the effect.
This is why gardeners wrap the trunks of maples and other vulnerable trees in winter, but that and the companion practice of whitewashing trunks seem to have fallen off. It would be nice to think that all those hip dudes in the city on electric scooters are racing home to wrap tree trunks. Honestly, I don’t think that’s the case. Trees must now look after themselves, something white birches figured out a long time ago – though not in my precinct, alas.