birch

The one tree that everyone seems to be able to identify is the white birch.

That is if you don’t look too closely or don’t get technical with the name. What most people think of as a White Birch is more properly called a Paper Birch – Betula Papyrifera. It’s the species with the big sheets of “paper” bark peeling off. There is another species that is common that is also white but is the Gray Birch – Betula Populifolia. Continuing the color theme is the Yellow Birch – Betula Alleghaniensis, and the Black Birch – Betula lenta. Betula nigra is called River Birch or Red Birch, but in my book of “North American Trees” Red Birch is also called Water Birch and only grows out west. This is not a genus for the color blind.

You should already be reaching for your favorite tree guide. I doubt there are as many tree guides as there are bird guides, but there are plenty. I own at least six, but two recent additions are my favorites. One is “Forest Trees of Vermont” by Derby Tree Farmer Trevor Evans. It features good photos, handy comparison charts, and if you’re into keys, it has both winter and summer keys. If that’s not enough, this ring-bound book is published by Forestry Press, appropriately located in Old Hickory, Tennessee.

The second guide you want is “Bark – A Field Guide to Trees of the Northeast” by Michael Wojtech. Michael knows his stuff and if you are (or aspire to be) a Bark Geek, his introductory chapters on bark structure and type are great fodder. As you may have noticed, for eight months of our year we don’t have leaves handy, so being able to recognize bark is extremely helpful. This book does its best with photos of young, mature, and old bark of each species. It’s not fool-proof because bark can be quite variable within a species, and hybridization can smear the distinctions.

Let’s get back to birches. Luckily there are only three species that commonly occur in the forests of the NEK. Paper birch is the whitest and with those big sheets of bark that peel off as the tree grows it captures our attention. Paper birch is bright white for a reason. We are actually in the southern tier of its range, and it grows way up into the arctic, where it can survive temperatures of 60 below zero. On a sub-zero day when the sun is shining the south side of a tree can be quite warm. Dark bark can heat up dramatically, only to be quickly frozen solid when the sun goes down which can be fatal to the cells of the cambium layer just under the bark. The white color of Paper Birch reflects the sun and helps the tree maintain a consistent temperature under the bark.

All trees have lenticels, small pore structures that allow the exchange of gases with the outside air. The little horizontal lines on Paper birch bark are lenticels. Paper Birch lenticels are structured to let in water vapor but not let it out as a way to conserve moisture. This characteristic plays into the use of birch bark for canoes. Natives covered canoe frames with birch bark for a few reasons. First was the fact that it will hold water, largely due to the oil content in the bark, which is also what makes it a great fire starter. The fact that the lenticels in the bark are one-way paths for water means that you want the white side facing the interior of the canoe. And I’m sure the ability to peel large intact sheets, which meant fewer seams, made it more efficient to seal it up. A compound called betulin is present in Paper Birch bark. Betulin resists bacteria, fungi, and insects which made the bark a good vessel for food storage.

Paper Birch is a moderate-sized tree but can live over 100 years and grow over 75 feet tall. Growing in the woods surrounded by close neighbors it grows straight up, shedding branches quickly as it reaches ever higher, and developing its classic long clear trunk. But like all trees, if a Paper Birch grows on the edge or out in the open it will get branchy and look quite different, easily confused with Gray Birch.

Gray Birch (also called black birch by some folks) is not as cleanly white as Paper Birch. It doesn’t grow up in the Arctic so doesn’t need to survive extreme cold. The lenticels are dark and Gray Birch bark develops prominent dark triangular patches at branch scars, which is a reaction to a fungus. This species is a true pioneer, growing quickly and prolifically in clear-cuts. It grows lots of branches and thus has lots of these dark patches. The bark hardly peels at all. It generally grows only about 30 feet tall and dies within 50 years as true forest species take over.

Yellow birch with its distinctive golden bark is an easy tree to pick out when looking through a forest. The bark peels in delicate strips and contains oil of wintergreen, making it another good fire starter. You can taste the oil by chewing on a twig. The wood has good characteristics for furniture including attractive reddish heartwood, making it one of our valuable hardwoods. It grows best in slightly wet soil, can live over 300 years, and can attain impressive girth. Eventually, the bark of Yellow Birch loses its bronze hue and its peels and develops a rugged platy bark that makes it look like an old sugar maple. My favorite characteristic of this species is its proclivity for sprouting on top of something. In undisturbed stands, yellow birch can best regenerate on mossy logs, decayed wood, rotten stumps, cracks in boulders, and windthrown hummocks. This is because its delicate root structure cannot penetrate hardwood leaf litter on the forest floor before it desiccates and dies. The seed that lands in a shady, mossy, moisty spot is the one that will have a chance. Then the growing tree can send roots down into the mineral soil at the base of the stump or boulder. When the stump rots away, the Yellow Birch tree remains, supported by roots that reach up in the air, looking like stilts. On a boulder the roots curl their way down, growing bigger each year to the point where the tree appears to be sitting on the boulder-like an egg, roots fondly hugging rock.

The fourth Vermont birch is Betula lenta, Black Birch. This tree has dark bark from the beginning, and when mature the bark resembles Black Cherry, hence the other common name, Cherry Birch. Black Birch is common in central and southern New England, where it can attain heights over 100 feet.

Common yet distinctive, the varied birches of this part of the world are worth.