There are 34 species of birch trees that can be found growing in North America, according to the United States Department of Agriculture (USDA). Some are small shrubs, while others are towering trees. Some birch trees have bark that turns white as the tree ages, while others have white bark that turns black as the tree gets older. While they can vary widely in appearance and culture, birch trees do have some similar characteristics regardless of the species.
Shallow Root Systems
All birch trees have very shallow root systems. For this reason, they prefer cool, moist soil. The constant moisture of the soil makes it very easy for the roots to uptake the water. In fact, birch trees are known for needing a lot of water compared to other trees. The shallow root system also makes the trees quite fragile. They will often topple easily in a wind or ice storm.
Birch trees tend to have short lives. While some varieties are hardier than others (the paper birch is known to be quite hardy in cold climates), most birch trees have an average life expectancy of only 10 to 15 years. One of the causes of early death is the fact that the shallow roots can girdle (encircle and choke) the trunk of the tree. Another reason is that these trees are very susceptible to insect pests (especially boring insects) and diseases that can greatly weaken this already fragile tree.
Birch trees are well-known for their attractive bark. Many have white or silvery-gray bark that peels off the tree in attractive rolls. Others have smooth, cream-colored bark that never peels. Regardless of the species of birch tree, the bark is quite distinctive and unusual.
The leaves of birch trees are small, graceful and delicate. In a breeze, they will rustle together pleasingly. Some varieties have almost lacy leaves, while other birch trees have small, teardrop-shaped leaves. No matter the shape, the leaves of all birch trees will turn a golden yellow color in the fall.
Warm Sun, Cool Soil, Plenty of Space
All birch trees need exposure to sunlight in order to thrive. Ironically, they also need cool, moist soil. If the soil is too dry and the sunlight too hot, the tree will quickly die. Also, if the soil contains too much standing water, the shallow roots will rot. The best location for any birch tree is in an area that receives morning sun with afternoon shade and well-draining but moist soil. In addition, birch trees need a lot of space to spread out. While they do not grow extremely tall (most average around 40 feet) they have a canopy that spreads twice as wide as their height.