Five species of Birch that are not hybrids and three hybrids are native to Minnesota. The Garden hosts four of those species of Birch, and once had one of the hybrids and one non-native species. The four remaining natives are Bog Birch, Paper Birch, River Birch and Yellow Birch. Absent is Sweet Birch which Eloise Butler planted back in 1910. The others are indigenous to the Garden except for River Birch which is native to parts of southern Minnesota and made its entry into the Garden in 1925.
The Bog Birch, Betula pumila, is a wetland shrub of the the northern tier of states in the U.S. and at higher elevations further south in the west, then north well beyond the arctic circle. It is food for wetland browsers.
The birches are all lovely trees look at - the White with its chalky barks separating in strips; the River with its irregularly peeling papery scales; the yellow with its smooth shiny reddish-brown bark that separates into papery curly strips and with age becomes tan to golden-yellowish - all providing Winter visual interest as well.
The White Birch, also known as Paper Birch, Betula papyrifera, is most well known to us in Minnesota. Prior to 1960 there was an extensive birch grove in the Garden. Eloise Butler wrote: “One of my white birches on a hillside has eight bolls, while opposite in the meadow a yellow birch rejoices with seven.” (1) Changes in the Garden from climate changes, the amount of water flowing through and changes in the tree canopy have greatly reduced the number of Paper Birch compared to what you see in the accompanying historical photo shown below.
Our most well-known use of the Paper Birch was for canoe covering. Francois Michaux explains how it was done:
"To procure pieces, the largest and smoothest trunks are selected: In the Spring two circular incisions are made several feet apart, and two longitudinal ones on opposite sides of the tree; after which, by introducing a wooden wedge, the bark is easily detached. These plates are usually ten or twelve feet long, and two feet nine inches broad. To form the canoe, they are stitched together with fibrous roots of the White Spruce, about the size of a quill, which are deprived of the bark, split, and suppled in water. The seams are coated with the resin of Balm of Gilead. Great use is made of these canoes by the savages and by the French Canadians in their long journeys into the interior of the country; they are very light, and are easily transported on the shoulders from one lake or river to another, which is called the portage. A canoe calculated for four persons with their baggage weighs from forty to fifty pounds.”(2)
Below: The extensive stand of paper birches in the Garden wetland on Oct. 30, 1948. Photo from a Kodachrome taken by former Curator Martha Crone. (3)
Michaux then describes the colonial uses of the River Birch, Betula nigra: "The epidermis of this species, like that of the Canoe Birch [B. papyrifera], divides itself transversely into thin, transparent sheets, which appear to be composed of a mixed substance, instead of presenting a pure, homogenous texture; hence they have not a uniform transparency nor a perfectly even surface: compared with the bark of the Canoe Birch, they are like coarse paper compared with fine. . . . In Philadelphia its twigs are exclusively chosen for the brooms with which the streets and court-yards are swept, which are similar to those employed for the same purpose in Paris. The twigs of the other species of Birch, being less supple and more brittle, are not proper for this use.” (2)
Today the River Birch is extensively used in landscape plantings as it forms a large tree and is long-lived. Those old ones remaining in the Wildflower Garden are of great size.
The Yellow Birch, Betula alleghaniensis is also a large tree but not used for most landscape plantings as it requires a moist habitat, but it had its important uses as lumber for ship parts and from its bark was extracted in great quantities Birch Oil, or Oil of Wintergreen, used to flavor candies and medicines. This function is now replaced by synthetics.
This takes us to our absent non-native species, the Sweet Birch, Betula lenta, which Eloise Butler had brought into the Garden from a source on the East Coast. The fresh cut wood has a rosy hue and took a brilliant polish on furniture. This species was a more prodigious producer of Oil of Wintergreen that was the Yellow Birch. The sap of the tree could be taped in greater quantities and with a faster flow rate than that of the Sugar Maple. It boiled like Sugar Maple sap but was stronger in taste - like molasses. (2)
The neatest use of the sap was for Birch Beer. "To every gallon whereof, add a pound of refined sugar, and boyl it about a quarter or half an hour; then set it to cool, and add a very little yeast to it, and it will ferment, and thereby purge it self from that little dross the liquor and sugar can yield: then put in in a barrel, and add thereto a small proportion of cinnamon and mace bruised, about half an ounce of both to ten gallons; then stop it very close, and about a month after bottle it; and in a few days you will have a most delicate brisk wine of a flavor like unto rhenish. Its spirits are so volatile, that they are apt to break the bottles, unless placed in a Refrigeratory, and when poured out, it gives a white head in the glass. This liquor is not of long duration, unless preserved very cool.” (4)
If you have the room, grow a few of these trees - even the Sweet Birch will grow well in central Minnesota.
The native species of Birch found in Minnesota, that has never been in the Garden, is Heart-leaved Birch, Betula cordifolia. It is rare in Minnesota, found only in the three counties of the Arrowhead. We are on the very NW tip of the plants range. It is mostly found around the Great Lakes region. Except for the leaf and a few genetic issues, one would mistake it for the White or Paper Birch, but it is usually occupies higher ground that the Paper Birch. The native hybrid that Eloise Butler found in the wetland in 1925 is Sandberg's Birch, Betula sandbergii [papyrifera × pumila]. The scientific name tells you it is a hybrid of the Bog Birch and the Paper Birch. The Minnesota DNR does not track the distribution of the hybrids in their plant census but we will assume Eloise identified it correctly.
Below: A comparison of the leaves of the five birch species detailed in this article.
(1) Annals of the Wildlife Reserve, 1915, unpublished.
(2) Michaux, Francois Andrew– The North American Sylva or A Description of the Forest Trees of the United States, Canada and Nova Scotia, Vol. II, 1820 and later editions.
(3) Photos by Martha Crone are from her collection of Kodachromes that was given to the Friends by her daughter Janet following Martha's death in 1989.
(4) Vinetum Britannicum, John Worlidge, London, England 1678