Wednesday, March 23, 2016

Birch, Sweet Birch - New England's Forest Birches

Bob Leverett and Black Birch

During his several decades of measuring and documenting the remaining old growth forests of eastern America, Bob Leverett began to notice a discrepancy. The commonly used tree reference sources (field guides, internet sites, etc)  report that black, or sweet, birch (Betula lenta) typically attains maximum heights of anywhere from 40 to perhaps 80 feet or so (depending on the source). But Bob was routinely finding black birches in Massachusetts that exceeded 80 feet. In fact, he and others have documented them at well over 100 feet high.
Bob Leverett Measuring an Old Black (Sweet) Birch
Bob Leverett measures Black Birch

Being a retired engineer and mathematician, Bob is a numbers guy. The discrepancies didn't set well with him. The record had to be corrected! And since Bob is a co-founder of the Native Tree Society, a national web-based group of like-minded tree measuring afficionados, he put out the call for everyone to seek out and measure the black birches in their environs. And he continued to do the same, to build a database of birch statistics here in central New England. The results clearly show that black birch quite easily exceeds the paltry 40-foot mark, and handily overtops the 80-foot level as well. In fact, we have many 90+ foot birches in western Mass, and some topping 100.

Smooth Bark of Young Black Birch (Betula lenta)
Typical young black birches

The Old Black Birch

Two or three years ago, Bob got me excited about helping to set the black birch record straight. I recalled a particularly old, fat one we saw many years ago on one of my first hikes with Bob and his son Rob, on the Mt Tom range in western Mass. It didn't resemble at all the beanpole black birches I had known up to that point. I was immediately taken with its look of great age, and I never forgot it. So I was eager to learn more about these sweet birches, and to help promote more appreciation of the older ones we have.

Finally, after several attempts to locate the big Mt Tom birch of my memory, I finally succeeded one day, in 2014. It was like finding the prize on a treasure hunt. It was still there in the forest, and I felt a real excitement at being next to it again, as though it was an old friend I thought had passed away years ago. 

So we began to re-explore some of the more mature forests in the area, happily measuring, documenting, and photographing the black birches, to defend their honor. After more than a year-and-a-half of that pursuit, it's very clear that the black birch's growth potential is widely under-reported. Why?

One reason may be because black birch hasn't been allowed to grow to anywhere near its full potential in most New England forests for a long time now, except in those places where cutting doesn't occur. 

Big Black Birches of the Past

The large, old birches of yesteryear were taken down long ago to become furniture, cabinets, and flooring. It takes at least 150 years for them to become large enough in girth to be particularly attractive to the lumber industry. So commercial forest managers, who generally prefer to keep forests on a roughly-60-year rotation, usually now harvest it before it ever has an opportunity to show its potential. It's not deemed economically justifiable to allow a tree to take well over a century to earn its keep. And that's understandable in today's context. But it's lamentable. 

 And there's more history that adds to the story. If you scratch the thin bark off a twig of black birch (or yellow birch), you'll be able to sniff the delightful aroma of wintergreen. That was discovered long ago, and led to the demise of countless young sweet birches. Oil of wintergreen (methyl salicylate) was distilled from the tree (after it was cut down and parts pulverized, of course), as late as the 1950's in some areas. The oil was used as a flavoring agent in foods and medicines. Black birch trees of any size actually became uncommon in some locales. And since it takes so long to grow to, say, a couple feet in diameter, large and old ones are hard to find today. But they're on their way back in forests that have been protected for a long time. In fact, they're filling in the voids left by the disappearance of the American chestnut, hemlock, and even oaks killed off by gypsy moths.

Black Birch Bark Breaking into Plates
Bark broken into curling plates

The Cornflake Bark of Very Old Black Birch
A very old black birch

Growth Habit of Black Birch

Black birch is a bit peculiar in its growth habit. Being intolerant of shade, when it manages to get a start in a forest clearing it shoots up quickly toward the light. Often this plays out where a fallen tree opens a hole in the canopy, allowing enough light to reach the birch seedling and get it going. The sapling birch rapidly becomes a spindly pole of perhaps 5 to 10 inches in diameter as it climbs ever closer to the canopy. This is the black birch diameter range that most people experience in New England, and elsewhere. At this stage of its development, the dark gray bark is either still smooth, or is somewhat cracked and/or broken into large plates whose edges curl away from the trunk. As time goes by, the curled edges of the plates break off, leaving narrowed plates. With greater age, new bark layers under them emerge, and go through the same process of stretching, cracking, and breaking up. But each successive bark layer starts off looking more mature and dull than the original, somewhat shiny sapling's bark. With enough time, the bark attains a thickly plated look that some describe as "cornflake" bark, which is reminiscent of old black cherry or even spruce or pine bark (in fact, another common name for B. lenta is "cherry birch"). Birches that old are rare in New England, so very few people recognize the tree at that stage. Some of the finest examples of old, big, black birch in all the northeast are found in the Mt Tom and Mt Holyoke ranges in the Pioneer Valley of western Massachusetts.

The Forest Birches of New England Video

Back to Bob... 

Well, if you're at all interested in trees, he's got a way of getting you fired up about big and old ones. It's infectious. Since I already had that bug, the fire was already burning. We spent a lot of time wearing out knees on steep terrain to find those full figured birch beauties. Since I was also interested in photography (especially of the motion variety), and Bob was eager to get the black birch record corrected, I suggested we tell its story with a documentary video. Didn't have to say it more than once. So we began that project in September, 2014. It would take a lot of time, and meant revisiting several places where we had found and measured exemplary sweet birches, but that was just fine. Then one day, Bob had the grand idea that "maybe we shouldn't limit the video to black birches; why don't we include all the birch species in New England?". Um, uhhh, ok. I guess. (I now think it's to my benefit to keep him so busy and tired that he can't think up new projects. He's relentless.).
Black Birch Tree Roots on Tiptoes
Black Birch on tiptoes

Black and yellow birches are arguably the most artistic in their growth habits. They often sprout from seed atop rotting stumps. They send their roots down the sides of the stumps, eventually creating the look of "trees on tiptoes" once the stump fades away. Yellow birches seem to have an affinity for boulders on steep, moist, old-growth forest mountainsides. Their roots wrap around the rocks, like a raptor's talons grasping prey.
Yellow Birch Growing on a Boulder
Yellow Birch on boulder

Well, that video is finally done. It took trips literally across the state, to the Merrimack river area near Boston (ugh) to film river birch (B. nigra), and to the Deerfield river gorge in the northern Berkshires (yay!!) for yellow birch (B. alleghaniensis). Covered in the film are white, gray, river, black, yellow, and heart-leaf birches, although the focus (pardon the pun) is on the forest birches (black, white, yellow). All in all, it really was great fun, and we have similar ideas for other tree species.

You can watch the video on Youtube here, or watch the embedded version below. Let us know what you think.