Birch Varieties Explained

The Wood Doctor lists the various species of Birch tree in North America and relates them to lumber for sale on the market. July 12, 2013

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I have a job where I need to fabricate some new trim work for a house that's all birch with either a light stain, or probably more likely a natural poly finish, that's darkened over time. So I've been trying to determine which type of birch it is. My problem is the information I'm finding on the net is contradictory.

For instance, one website says that red birch and yellow birch are both from the same tree. One is the sapwood and the other the heartwood. The next website says they're completely different trees, with different average sizes, color bark, etc.!

So what the heck is the truth about birch? Are white, yellow, and red birch different species? Are they different parts of the same tree?

The backside of the original trim on the house is much darker than, say, the birch veneer common on plywood, which I was always told is white birch. So I'm guessing it's red birch? But before I call my supplier and have them pull down a pack of something, I figure I better ask here first.

Forum Responses
(Architectural Woodworking Forum)
From contributor M:
It's probably yellow birch. From what I understand, it's the most abundant species (Betula alleghaniensis) in North America. At least that's the case here on the central east coast. But its range goes all the way west to Minnesota. I got that from Wikipedia.

From contributor B:
I've always been told that yellow and red are the same tree - sap and heart.

From Professor Gene Wengert, forum technical advisor:
When talking about commercial North American wood, there are three birches - paper (Betula alleghaniensis), sweet (B. lenta) and yellow (B. papyrifera). The heartwood of yellow birch is reddish and so sometimes the heartwood lumber is called red birch. Note that the red birch is only applied to lumber. (There is an uncommon birch tree that is sometimes called red birch.)

Two minor North American birch species are river birch and gray birch.

Sweet and yellow are very close in properties. Paper is much weaker. As an example, the hardness of paper is 910 pounds; sweet, 1470; and yellow, 1260. Paper is also about 15% lighter weight.

From contributor A:
In my experience with birch (not extensive, as I'm in the southeast US) if you want a color match, you are going to have to pick it out yourself. My suppliers will sometimes have separate packs of mostly sap (called "yellow" or "white") and with heart coloration (called "red"), but sometimes they are all in the same pack (called "yellow"). It is a subjective color-only denomination; it's not an indication of species. I treat a birch project like a black walnut project; lots of color matching.