How to Identify Common North American Birch Trees

Birch bark, leaves, fruit and range
River Birch and Range Collage. Wikicommons (GooGoo85 and Greg Hume, USFS

Basic Species Description

Most everyone has some recognition of the birch tree--a tree with light-colored white, yellow or grayish bark that is characteristically marked with long horizontal lenticels and often separates into thin papery plates. Birch species are generally small- or medium-sized trees or large shrubs, mostly found in northern temperate climates in Asia, Europe and North America. The simple leaves may be toothed or pointed with serrated edges, and the fruit is a small samara--a small seed with papery wings.

Many types of birch grow in clumps of two to four closely spaced separate trunks. 

All North American birches have double-toothed leaves and are yellow and showy in the fall. Male catkins appear in late summer near the tips of small twigs or long shoots. The female cone-like catkins follow in the spring and bare small winged samaras drop from that mature structure.

Birch trees are sometimes confused with beech and alder trees. Alders, from the family Alnus, are very similar to the birch; the principle distinguishing feature is that alders have catkins that are woody and do not disintegrate in the way that birches do. Birches also have bark that more readily layers into segments; alder bark is fairly smooth and uniform. The confusion with beech trees stems from the fact the beech also has light-colored bark and serrated leaves. But unlike the birch, beeches have smooth bark and they tend to grow considerably taller than birches, with thicker trunks and branches.

 

In the native environment, birches are considered "pioneer" species, which means that they tend to colonize in open,  grassy areas, such as spaces cleared by forest fire or abandoned farms.  You will often find them in meadowy areas, such as where cleared farmland is in the process of reverting to woodlands.

 

Interestingly, the sweet sap of the birch can be reduced into syrup and was once used as birch beer. The tree is valuable to wildlife species that depend on the catkins and seeds for food,  and the trees are an important timber for woodworking and cabinetry.

Taxonomy

All birches fall into the general plant family of Betulaceae, which are closely related to the Fagaceae family, including beeches and oaks. The various birch species fall into the Betula genus, and there are several that are common North American trees in natural environments or used for landscape design purposes. Since in all species the leaves and catkins are similar and they all have very much the same foliage color, the main way to distinguish the species is by close examination of the bark. The four most common birch species in North America are described below: 

  • Paper birch (Betula papyrifera). Also known as canoe birch, silver birch or white birch, this is the species more widely recognized as the iconic birch. In its native environment, it can be found in forest borders across the northern and central U.S.  Its bark is dark when the tree is young, but quickly develops the characteristic bright white bark that peels so readily in thick layers that it was once used to make bark canoes. The species grows to about 60 feet tall but is relatively short-lived. It is susceptible to borer insects and is no longer used widely in landscape design due to its susceptibility to damage. 
    • River birch (Betula nigra). Sometimes called black birch, this species has a much darker trunk than the paper birch, but still has the characteristic flaky surface. In its native environment, it is common to the eastern 1/3 of the U.S. Its trunk has a much rougher, coarser appearance than most of the other birches, and it is bigger than the paper birch, sometimes growing to 80 feet or more. It prefers moist soil, and although short-lived, it is relatively immune to most diseases. It is a common choice in residential landscape design. 
    • Yellow birch (Betula alleghaniensis). This tree is native to forests of the Northeast U.S. and is also known as the swamp birch due to the fact that it is often found in marshy areas. It is the largest of the birches, easily growing to 100 feet in height.  It has silvery-yellow bark that peels in very thin layers--not the thick layers seen in paper birches, nor the very rough texture seen in river birches. 
    • Sweet birch (Betula lenta). This species, also known in some areas as the cherry birch, is found native to the eastern U.S., especially the Appalachian region.  Growing to 80 feet, it's bark is dark in color, but unlike the river birch, the skin is relatively tight and smooth but with deep vertical scores. From a distance, the impression is of a smooth, silver bark marked by irregular vertical black lines.