Birches

I had been thinking that birches that are white and peeling are paper birch, and birches that are white and smooth are gray birch.  Around work, I often see trees with bark which is white and peeling, so I thought they were paper birches.  However, I noticed that they had a reddish tint to them, which was different from the paper birches I saw growing up.  So I looked in the books, and it seems they are called river birches or red birches.

Commonly found types of birches:

• Gray birch, white birch, oldfield birch: Saplings have dark reddish brown bark with lighter lenticels. Older trees have white or gray bark, with black patches.   Tends to be smaller tree than other birches. Smaller catkins. Catkins tend to be individual rather than in clusters. Leaf is triangular. 
• Paper birch, white birch, canoe birch, silver birch: Saplings have dark reddish brown bark with lighter lenticels.  On older trees, usually bark is white and peeling, but some may retain the reddish, unpeeling bark typical of younger trees. Larger catkins. Leaf rounded, with pointy tip. 
• Black birch, sweet birch, cherry birch: Young bark is smooth, old bark is scaly. Larger catkins. Leaf resembles elm. Twigs have wintergreen odor.
• Red birch, river birch: Young bark is peeling, reddish, yellowish, gray.  Old bark is scaly, gray.  Smaller catkins. Commonly cultivated. In the wild, grows in southeastern US on stream banks and river floodplains.
• Yellow birch, gray birch, silver birch, swamp birch: Younger trees have bronze bark which may or may not be peeling.  Older trees have gray plated bark that may peel. Larger catkins.Leaf resembles elm.

Yesterday as I drove through Massachusetts and Connecticut, I saw a lot of trees with white bark.  I saw similar trees when I was in Maine a few months ago.  I do not see this kind so commonly around where I live.  These trees have white bark, but it does not seem to be peeling.  Maybe that means they are gray birch.  Or maybe they are paper birch, and maybe paper birch is not necessarily noticeably peeling, especially when seen from a distance.

Maine last December:

River birches at work:

Sources:
Sibley, David Allen.  The Sibley Guide to Trees.
Symonds, George W. D.  The Tree Identification Book.