Friday, November 16, 2012

The birch with non-acuminate leaves

Species name: Betula pendula

Common name: Weeping birch, silver birch

Location: Ontario

The weeping birch, usually having typical birch-shaped leaves ("acuminate" shaped leaves), is a common species in Europe and Asia throughout its native range and is often called the silver birch because of the bright white or silverish bark of the trunk of the tree. This particular tree is a certain type of weeping birch called the "cutleaf weeping birch", named after its very pronounced toothy leaves. There was once the suggestion that they should be different species because they are so morphologically different (the only real thing they have in common is the general shape of the tree; if that was all that was needed to determine species we would only have about 6 species of trees!), but this idea has been abandoned now that we know how genetically similar they are. There isn't enough variation in the barcoding regions of their genomes to allow for a separate species designation.

The first thing that many Canadians think of (if you're born before 1990 and/or was a member of boy scouts or girl scouts) when they hear "silver birch" is the camp song called "Land of the Silver Birch." To this day, I can still remember every single word! Unfortunately, that song has nothing to do with this tree. The song actually refers to the paper birch, the one from which birch bark canoes are made (which you can read all about HERE).

There are very few modern uses of the silver birch, although historical use of this tree was wide reaching. Currently it is used to make the poles for horse jumps since the wood is heavy enough to stay in place, but not too heavy to injure the horse if it hits the jump. They are also commonly used in the making of wooden utensils because of the attractive grain of the wood and the fact that it doesn't give off a flavour in the food like maple or oak wood would. In Europe the silver birch is popular in the pulp and paper industry, but in Canada we use other species primarily for this purpose. Historically, wine was produced from the sap of the tree, and that same sap could be condensed down and used as a type of glue. The bark was also popular for tanning leathers, especially when a light colour was desired (other barks or plant products were used if a dark colour was desired).