Birch

Birch Trees- Beautiful Bark, No Bite
By Kim Willis

Birch trees have been long been a popular landscape choice. There are species of birch growing throughout North America, Europe and temperate Asia. Birch trees have a graceful shape, interesting bark and good fall color. They are not the best choice for all landscapes but if the conditions are suitable, there are few trees prettier than a birch.

North Americans tend to think of birches as clumps of small trees with white peeling bark. These clumps were widely planted as landscape trees before the arrival of the Bronze Birch Borer. This destructive beetle attacks and kills many types of birch trees, but white barked birches from Europe are the most susceptible. However, there are many types of birch and some are very resistant to borers and are seldom attacked if they are healthy.

Birch trees are generally small, 20-30 foot and pyramidal in shape. There are some weeping varieties. Birch leaves are thick, glossy, dark green in a rough triangle shape. There are some cultivated varieties with purple or reddish leaves. Birch leaves are lighter on the reverse side, have serrated edges, and are arranged alternately. Some varieties have deeply lobed leaves with a lacy appearance. Fall color of birches is generally a good, clear yellow. Birch trees have both male and female flowers, the male flowers are long, dangling and generally in clusters of threes. The female flowers are much smaller and rounder. The pollen of birch trees is highly allergenic to people with seasonal allergies.

The bark of birch trees is the reason many are planted as landscape trees. When young most birch trees have brown bark but as some age they may get various shades of white, yellow, or red bark that peels and curls, revealing contrasting colors beneath it.

Birch grows easily from seed but most gardeners will start with small trees. Birch trees are best planted in early spring. If you want a clump of birch trees you can buy several small trees and plant them in the same hole or you can buy trees in pots which have several stems.

Birches are trees of the forest edge and riverbanks. They like cool shaded soil at their feet and their heads in the sun. Most birches prefer cooler climates, from zone 3 to zone 6, but there are a few species that tolerate warmer zones. Birch trees have shallow root systems and don’t do well in dry areas. They do not do well in alkaline soil, [a ph of 6.5], or higher, so a soil test before planting birch trees may save time and money. Good places to plant birches are the north and east side of homes or out buildings, windbreaks or tree lines. Birches should be planted where they can be watered during dry periods. Although they need moisture, most birches will not thrive where the soil is always wet. The River Birch is a little more tolerant of wet conditions. Don’t plant birch trees where they will have to be frequently pruned, birch bleeds profusely when pruned and the wounds attract the Bronze Birch Borer. Prune birch trees only during the time they are dormant. If the trees are damaged during the growing season apply a registered insecticide; not tree paint, to the cut surface. Keep children from peeling away large areas of bark, they hear many stories about birch bark and often want to experiment. This may damage the tree or attract insects.

Mulch birch trees after planting with about 3 inches of organic mulch to conserve moisture and cool the soil. Birch trees should not be planted where salt used on sidewalks or roads in winter will run off around the root system. Birch trees are not good trees for parking lots or other areas where they are surrounded by pavement.

Birch trees also attract an insect called a leaf miner. This insect lays eggs in tiny slits on the leaf surface and the larvae that hatch tunnel between the two leaf surfaces. The leaf turns brown and falls off. While leaf miners don’t kill the trees, they make them look very unsightly and may weaken a stressed tree even further. Using systemic insecticides can control both the Bronze Birch Borer and leaf miners. Homeowners have several products that they can use. Contact your local County Extension Service for their recommendations in your area.

Choosing Varieties

Varieties with white bark are more susceptible to Bronze Birch Borer but these varieties have been bred to be resistant, ‘Whitespires’, ‘Renaissance Reflections’, ‘Rocky Mountain Splendor’. River birch, Betula nigra, is tolerant of heat and wet conditions and somewhat resistant to borers. ‘Heritage’ is a selection of river birch that is even more resistant. River birches have light gray bark, peeling to show white, pink, and brown underneath. ‘Summer Cascade’ is a weeping birch reaching about 10 foot tall, ‘Filigree Lace’ is a cut leaved dwarf birch, ’Royal Frost’ is borer resistant and has burgundy foliage until fall, when it becomes orange. Betula lenta, Sweet Birch, has smooth mahogany red bark that does not peel, and its leaves have a clean, pleasant scent.

Using Birch

In the right place the birch is a lovely tree, with good fall color and interesting bark in the winter. It provides light shade for plants like hosta and ferns and likes their company at its feet. Many species of butterfly larvae eat the leaves of birch.

Birch trees had many uses by indigenous people. They were used in religious and magical rites, and birch bark was used for some of the earliest writings. The bark is full of oils that help preserve it and many artifacts hundreds of years old made with birch bark have been recovered. Besides the famed canoes, birch bark was used for roofing, native houses, baskets and bowls, paper, and even clothing. The oily wood is excellent for fire starting. The sap of some types of birches is boiled into syrup like maple syrup and also made into wine and vinegar. The small nutlike seeds were also used as food.

Copyright Kim Willis 2008