While spring is just around the corner, it will be a while until leaves emerge from buds and the Arnold Arboretum takes on the deep green hue of summer. In the meantime, aside from our evergreen trees and shrubs, you can get an interesting and aesthetically pleasing dose of green in the form of bark. Green bark is far more common than you might imagine. Every smooth barked tree has a significant photosynthetic layer of tissue that is capable of recycling (respired) carbon dioxide from the woody tissues and producing sugars when the sun is out.
While some photosynthetic bark is totally obvious, as is the case with Acer tegmentosum, the Manchurian striped maple (20848*A; top), and Pinus bungeana, the lacebark pine of China (466-80*A; bottom left), you might be surprised to learn that under the outer smooth barks of birches and stewartias, there is a bright green layer of photosynthetic tissue too! On the bottom right, I peeled away a small bit of the outer bark of Betula populifolia, the North American gray birch (595-2008*B), native to most of New England.
Another and familiar maple that displays striped green and white bark is Acer pensylvanicum, the moosewood or striped maple, native to New England. This species belongs to the same section of the maple genus as Acer tegmentosum and is a great example of an eastern Asia – eastern North America disjunct pattern of biogeography.