Birch trees in North America belonging to the family Betulaceae share similar traits. Many are ornamental species that homeowners choose for a number of reasons. Some birches possess attractive qualities such as colored and peeling bark, a manageable height and colorful leaves come fall. Birch trees require specific conditions in which to grow and suffer from certain types of pest infestations more frequently than other species.
Among the native birches to the United States and Canada are species such as paper birch, river birch, yellow birch, water birch and sweet birch. Introduced birches from other nations include the European white birch. Cultivars of native birches, enhanced to showcase certain aspects of the tree, include those like Snowy, a paper-birch hybrid, and Cully and Little King, popular river-birch hybrids.
Birches possess simple leaves that fall off the tree before winter. The leaves are alternate, growing one per node on the twigs. Birch leaves are typically oval to elliptical in terms of their shape. Most are a shade of green and can change to such colors as yellow, brown and bronze in the fall. The flowers that develop in the spring, called catkins, are of the male and female variety on the same tree.
The height of birch trees fluctuates, depending on the type. The paper birch and the yellow birch can easily top 80 feet. Sweet birch usually is in the range of around 60 feet tall under good growing conditions. Smaller birches include the water birch, Yukon birch and gray birch, which all grow to around 20 to 30 feet in height.
Birch trees normally require full sun and moist ground in which to grow. The National Forest Service website states that most birches growing in the wild do so in cool moist ground. The root systems are shallow, making the birch susceptible to problems when droughts occur. To get the most sun but still maintain a damp and cool environment for your birch to grow in, try planting it on the eastern or northern side of your house. The house can give it shade from the hottest rays of the afternoon sun.
The bronze birch borer is a beetle species that produces larvae that bore into a birch tree. This interferes with sap flow and causes problems for the birch. A tree suffering from this pest will have a crown thinner than a normal birch, as nutrients fail to reach it. The larvae of the birch leafminer also will tunnel into the bark and wood, disrupting nutrient flow. The leaves can turn prematurely brown when this insect infests a birch. Sap-sucking aphids such as the common birch aphid also can weaken a birch.
Choose a birch by the type of bark the tree will develop. Paper-birch bark starts out as a brownish color but turns chalky white as the tree matures. The bark will peel in long strips. Gray birch has a chalky whitish bark but this bark resists peeling. River birch has a multicolored bark that features colors like tan and pink along with silver-gray. Yellow birch has a yellow-orange colored bark that peels into curled-up strips.