Black Birch Bark
Richard Wilbur, A Black Birch in Winter:
You might not know this old tree by its bark,
Which once was striate, smooth, and glossy-dark,
So deep now are the rifts which separate
Its roughened surface into flake and plate.
Fancy might less remind you of a birch
Than of mosaic columns in a church
Like Ara Coeli or the Lateran,
Or the trenched features of an agèd man.
Still, do not be too much persuaded by
These knotty furrows and these tesserae
To think of patterns made from outside-in
Or finished wisdom in a shriveled skin.
Old trees are doomed to annual rebirth,
New wood, new life, new compass, greater girth,
And this is all their wisdom and their art—
To grow, stretch, crack, and not yet come apart.
The scientific name of black birch is Betula lenta; other common names are cherry birch and sweet birch. Charles Fergus, Trees of New England: A Natural History (Guilford: Globe Pequot Press, 2005), pp. 51-52, describes the bark:
The bark of sweet birch is dark brown to purplish black, smooth and shiny when young and becoming rough and plated with age; it does not peel off in papery layers like the bark of other birches, although sometimes thick flanges of it stand off from the trunk.
On p. 53 of Fergus' book there are excellent drawings by Amelia Hansen of the young and old bark of Betula lenta.
See also Forest Trees of Maine, 14th ed. (Maine Forest Service, 2008), p. 94:
The bark on the trunk of old trees is dark to almost black, and separates into large, thick, irregular plates. On young trees and branches, it is smooth, shiny, dark brown tinged with red, aromatic, and has a very pronounced wintergreen flavor.
:lol: 
