Betula papyrifera

Alaska has three kinds of tree birch and two kinds of dwarf birch (only the tree birches have the uses described here). The tree birches hybridize wherever they meet, so they are considered three geographical varieties of a single transcontinental species.

The white, paperlike bark of these trees separates into layers. The bark remains smooth as a result of its persistent cork. Twigs growing above the reach of browsing moose have a smooth bark, but the lower ones are covered with white bumps called lenticels. The lenticels are believed to be associated with defense against browsing herbivores.

Each alternately arranged leaf is round with a sharp point. Leaf margins are sharply toothed with teeth of two sizes. The flowers form catkins with long, narrow male and short female flowers. Conelike fruits have many nutlets, seeds, and scales. Winged birch seeds often cover the snow with their tan crosses.

Birch leaf
Birch leaf

If one includes the dwarf birch, Betula nana, the birch is distributed over all of Alaska except the very northern coast and the tip of the Aleutians.

The Merck Index cites betulin (betula camphor) 10% to 15% in the outer portion of the white bark. Leaves contain betuloresinic acid, essential oil, ether, betuloside, gaultherin, methyl salicylate, and ascorbic acid; in the bark of the sweet birch is salicylic acid.

Medicinal uses:
Margaret Lantis reports Natives using birch leaves to make a comforting tea. Birch leaf tea has been used as therapy for gout, rheumatism, and dropsy and also for dissolving kidney stones. Simmonite-Culpeper describes birch as a diuretic if a strong juice is made from the leaves. A decoction of leaves may be used as a mouthwash. According to Grieve the young shoots and leaves secrete a resinous substance that, combined with alkalis, forms a laxative.

A birch bark decoction can be used for bathing skin eruptions. The inner bark is astringent and bitter; it has been used to treat intermittent fevers.

Birch sap as medicine and spring tonic is bottled and sold in Russia. (L. Viereck, personal communication) Kari reports the Tanainas put fresh birch sap on boils and sores. The old way to obtain sap is to peel back the bark and scrape or suck the sap off the wood.


Culinary uses:
Birch sap can be boiled down to make a sweet syrup. My method of collecting birch sap is to use the equipment manufactured and sold to the maple syrup industry. The equipment consists of a spout that is inserted into a hole drilled into the tree, and a bucket that hangs from the spout to catch the sap as it drips out. I have made a ten-minute videotape documentary of this procedure, available from Teri Viereck, 1707 Red Fox Drive, Fairbanks, AK 99701. The price is $25.

If you want to drill a hole in a birch tree to collect sap, wait until the sap is flowing or the surface will scar over and reduce the flow. The sap may begin flowing any time from mid-April to mid-May. You can cut a small branch or drill a test hole to find out if the sap is flowing. Sap flow is the result of "root pressure"--that is, water is actively absorbed by the root system, but pressure builds because little water is lost from the tree as a whole. The sap flows the week or two before the leaves begin to open; once they are growing, the root pressure lowers. Near the end of the season the sap gets white, milky, and bitter due to yeasts.

Birch sap contains the sugars glucose and fructose, whereas maple sap contains mostly sucrose. Another difference is that birch sap is more dilute than maple --birch sap has only 1% syrup by weight.

To make a thick syrup, birch sap must be boiled down to decrease its volume by thirty or forty times, but maple sap (2.5% sugar) needs only twenty-five times concentration. It is very difficult to reach the syrup stage without burning the sap, so use a very very low fire, an asbestos pad, or steam (as in a double boiler) and watch it carefully. I have spent days of boiling and wound up with a bit of charcoal more than once. This year I let it go a bit too far over the cool end of my wood stove and obtained a delicious taffylike candy that tastes like molasses.

Some people use birch sap to make beer, wine or soft drinks.

Other uses:
A brown dye can be obtained from birch bark. The bark also yields oil of birch tar, which imparts durability to leather. The white epidermis of the bark can be separated and used as a substitute for oiled paper.

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Copyright © 1987 by Eleanor G. Viereck