Arboretum: Betula papyrifera, paper birch
Birches love the cold; they’re one of the few deciduous trees that grow alongside firs and spruce in northern climates. A key identification is the thin, colorful bark that peels off in strips as the tree matures. The paper or canoe birch, Betula papyrifera, has the lightest bark of all birch species with creamy white trunks that stand out in our gray winter landscape.
At Haverford College we don’t have to worry about moose nibbling on our paper birches as they do in New Hampshire where it’s the state tree, but we do deal with insects. The paper birch grows best in colder climates, is not tolerant of pollution and wants full sun. Therefore good specimens are hard to find growing here because of our summer heat and humidity that only encourage borer infestations and doom the tree to a short life.
A healthy tree can grow 50 to 70 feet tall. The small oval leaves end in a point and have toothed edges. Catkins, inch-long clusters of male flowers, dangle from the branch tips and are easy to spot in winter before they open on a breezy spring day and release pollen. Other trees that bear catkins are willows and poplars. The tree’s most prominent feature, the bark, slowly turns lighter and lighter as it grows, eventually adding black streaks on the oldest branches and the trunk. The bark is slow to rot, and a walk in the woods can reveal fallen trees with hollow cores where the wood has disintegrated and the curled bark remains.
The alternative common name of canoe birch refers to the Native Americans’ use of the tree. Today the wood has many commercial uses, including the manufacture of tooth picks and ice cream sticks.
A better suited birch to grow in our area is the river birch, Betula nigra, which has attractive tan and pinkish bark. Compare the cluster of ‘Heritage’ cultivars of Betula nigra planted between the Fine Arts Center and the Gardner Center or the specimen at the Carvill Arch, with the few Betula papyrifera trees at the college: one behind Roberts Hall, several in the Nature Trail woods across from the stream, and several just off Featherbed Lane, across from the softball field.