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Wednesday, October 29, 2014

The Big Search for Big Birch

We've all heard the old idiom, "You can't see the forest for the trees." But sometimes, we can't see the trees for the forest. Have you been for walks in the woods when you're too busy yacking, or so deep in thought about life's pesky burdens, that you take no notice of the individual trees standing sentry along your path?

That's understandable. Even those of us whose purpose in a sylvan safari is to seek out the finest, largest, and oldest stationary dwellers of the forest can sometimes be guilty of same. We might overlook a tree, rather than look it over.

Some twenty-five to thirty years ago, on one of my first jaunts with Bob Leverett and his son Rob (both zealots on the quest to find and document the biggest and best of each tree species east of the Rockies), I recall us descending a forested ridge in the Connecticut River valley and coming upon a fat, handsome tree I didn't immediately recognize. Actually, it might be that I didn't recognize it at all; that, I can't recall for sure. But the image of that tree stamped an impression in my memory that has lasted to this day. What was that tree? It was a black birch, Betula lenta, also commonly known as "sweet birch".
The young and familiar black birch

 I, like most others in the northeast, was accustomed to black birch being a bean pole of a thing, tall perhaps, but typically no more than 6 or 7 inches in diameter, occasionally maybe 10 inches. And instantly recognizable with its smooth, dark bark (any doubt could be removed by scratching the bark off a twig and sampling that wonderful wintergreen aroma).

Bob has spent every available moment of the last thirty-something years, and more, exploring older forests all over eastern North America, painstakingly measuring the tallest and biggest trees he can find. He was never much impressed with the spindly black birches so typically encountered here in New England. But, being especially tuned in to tree heights, he did take note that there are at least two places in Western Mass where they have attained much greater heights than most sources would have us believe. And the fact that the generally reported height statistics quoted for a tree species are inaccurate and understated finally weighed upon his conscience, I guess, and he has set out to correct the birch's record.

Bob, measuring Black Birch
If you consult field guides or internet sources, you'll likely find a range of maximum height specs for black birch of 40 to 80 feet or so. Well, 40 feet is ludicrous for a black birch max height; 80 is much more reasonable, given the current state of our typical second growth forests. But Bob and cohorts have already located many black birches that easily surpass 80 feet, and soar to well over 100 feet.

So this year, we've begun searching out the biggest and best of the Bay state's black birches. Bob is assembling a growth profile on the species. Other tree enthusiasts in the Native Tree Society are on a similar mission in other states. As a result of this hunt, several of us have come to appreciate the beauty of older specimens of this attractive tree. And that's what prompted me to write this.

The Past

Historically, black birch was valued for an extract of its wood known as oil of wintergreen, which was used as a flavoring agent. Enter modern chemistry: we don't need a forest anymore, just a well equipped food additive lab.

Its aromatic sap was fermented into birch beer. Not at the top of the beverage list these days.

Today, there's a bit of a resurgence of interest in tapping these trees to boil sap down to birch syrup, but it takes over 100 gallons of sap to make one gallon of syrup. Economics declares that a folly.

Black birch lumber was harvested heavily in days gone by, and many an Appalachian sawmill prospered from it. The wood, when aged or stained, was considered a substitute for mahogany by furniture makers, and led to a couple  of the tree's common names, "mountain mahogany," and "mahogany birch". In those now-nostalgic days, Appalachian cove forests were home ground to gorgeous virgin birches, which were quickly exploited. The big ones are gone.

The Second Growth


Black birch has a habit of rocketing upwards into whatever openings in the canopy there may be above it. Accumulating girth seems to be a secondary goal.
A left turn puts it in the sun up there

 It will bend and zig-zag its way up to flutter its foliage in sunlight, and it apparently can do that very quickly. When it has gained its place in the sun at canopy-top level, it slowly begins to put on girth, but it can be in the neighborhood of 150 years old or more before its diameter will impress anyone, particularly the lumber trade. That fact explains the relative lack of interest there is today in harvesting black birch for lumber... there aren't any left of large enough diameter to bother with! And it explains why, when we encounter black birches in the forest today, they usually don't command our attention. But time will change that, if we can refrain from culling them from our forests. Economically, it's difficult to justify granting trees a 150 or 200 year lifespan. But aesthetically, and ecologically, it's more than worth the wait.

Now that our virgin forests have been cut, the black birch we have today is mostly of small diameter, up to maybe 10 or 12 inches, occasionally a bit more. They may be rather tall however, due to their habit of soaring up to the canopy; that makes them appear spindly, for the most part. On these thinner trunks, the bark will still be youthfully smooth, or in the initial stages of breaking up into plates. This is the image most people today have of black birch.

There are, though, some places where they've had enough time to fatten up a bit, and acquire a more fitting stature. Those are the kinds of places we're searching. The older, larger trees sometimes tend to be in the kind of place that most people won't go: steep slopes and boulder fields, or at least off-trail in the less traveled woods. Black birches appear to be on the increase too, taking the place of some of the American chestnuts that have been wiped out by the blight. And with the loss of many hemlock stands to the woolly adelgid, the birches are gaining more territory there.

The birches have very tiny seeds, which require contact with mineral soil to successfully put down roots. They don't have the stored energy to sink roots down through the forest floor duff to reach soil. They therefore sprout on exposed soil, such as the "pillow" mound created when another tree is wind thrown and uprooted; or on the thin layer of "soil" that may have accumulated on a rock ledge or boulder. Sometimes on a stump.

A birch perch
Where'd the stump go?
When they've put their roots down on a pillow mound, it often happens that the exposed soil mound gets washed away from under the tree with a little time, leaving the growing tree "on tiptoes". Or, if on a stump, the stump rots away.
Yellow birches are famous for this, but it's not unusual to find black birches in the same comical predicament. More commonly, black birches seem to be drawn to boulders (at least in western Mass), often wrapping roots on and around them, seemingly
clutching the rocks tightly in their talons. We've seen so much of that, that I've taken to declaring "every black birch has its rock." If it isn't wrapping around the rock, it's at least standing right next to it. They can often be found growing out of the crevices of boulders.
Black Birch "on the rocks"


 Reading the Bark

A close look reveals that young black birch bark has a pattern of horizontal bumpy ridges, called "lenticels". These are pores that allow the tree to exchange gases with the atmosphere. The inner bark can carry on some photosynthesis, as the leaves do, and takes in carbon dioxide through the lenticels in the process, and gives off oxygen.
Lenticels on young tree

Bark beginning to split
As the young tree grows and adds to its circumference, its smooth bark is stretched and begins to split. The cracks expand with time and growth, breaking the bark into plates that tend to curl away from the tree at their edges. Lenticels can still be seen on the plates at this stage.
Lenticels still visible on curling plates

New bark is being grown under this initial layer, and can be seen between the plates. Many trees have a shaggy look as the plates slowly curl and slough off.

The shaggy look

Eventually, the curled, loose portion of the original plates are shed or eroded away. I suspect that the area of the plate that isn't curled away remains in place for a long time, resulting in a look of smaller, scaly strips. Each year, new bark tissue is added by the cambium layer under the existing bark (as in all trees), thickening the bark, and lenticels are no longer so apparent. With time, the bark takes on the look of the tree shown below ("A very old black birch").


An older black birch


A very old black birch

    On many older black birches, a wonderful greenish-blue color of algae and/or lichen appears on the bark, particularly close to ground level.
The greenish-blue look, and moss

Here and Now


Luckily, we in western Massachusetts have a small treasury of really handsome black birches, in at least several locations. There are plenty of sites with the typical young trees, those dusky black poles we're accustomed to. But then there's the exceptional trees that many probably wouldn't recognize as black birch. Their bark has been stretched by expanding girth to the point where the once-smooth skin is now cracked and broken into strips and plates.  A very few old trees we've found so far have aged beyond that stage, and the bark is more rugged looking, and tighter to the tree once again.

Black birch favors rich, moist soil, and so is generally found in cool Appalachian mountain coves and hills. The older, larger trees we've found in western Massachusetts often have symptoms of those cold, wet conditions, in the form of moss moccasins on their feet, and algae aprons on their hides. Set against the dark bark, the colors are stunning.

These trees, these special ones, are so much more pleasing in appearance than the youngsters. They've acquired that certain, yet uncertain, look. You can't quite describe it adequately, but these old-timers have seen some years, and they speak of that. They've survived the elements, having been shaped and colored by them. They lean, they recurve. They glow with cool hues. They spread their toes in moist leafy earth. They clutch the rocks in a tight grip on their precarious perches.

If you know where older black birches can be found in New England, we'd like to hear about them. Enjoy now some of the best we've been lucky enough to come to know ....

The Green Giant
Arnie Paye, Frank White measure a beauty
Barbara Bosworth, Bill Finn at 9.2 ft circumference birch
In an old growth Berkshires forest
Another old growth forest birch

Bill Finn admiring an old forest denizen on a talus slope

A tall black birch beauty in a cove

A black birch and its rock

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