University of Vermont
Department of Plant and Soil Science

Anytime News Article
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BEAUTIFUL BIRCH TREES

Dr. Leonard Perry, Horticulture Professor
University of Vermont

Birches are beautiful in all seasons, from the bright green leaves in spring and dangling flower clusters, the dappled summer shade, yellow fall colors, and the attractive bark of many in winter.  There are several species and popular cultivars (cultivated varieties) to choose from, some being native to Vermont.
   
Most have an upright, oval habit, but the European birch (Betula pendula) has weeping branches (pendula means weeping).  Reaching 30 to 40 feet high or more at maturity, birches are not for small landscapes, yet only one tree can be planted as a specimen if space—they often spread 20 to 30 feet wide or more.  Or, several can be planted in a mass, as you often see in commercial business plantings. Whether planting as specimens or in masses, consider underplanting them with perennials or groundcovers.
   
Birches are hardy to at least USDA zone 4 (-20 to -30 degrees F average winter low temperature), some to even colder temperatures.  They prefer sun, except for a few that also grow in part shade.  They prefer moist soils, but some tolerate ones that are dry and sandy. 
   
The bronze birch borer can be a problem on some species—the larvae of this insect killing tree tops and perhaps whole branches through its feeding in the bark—but other species are resistant to it.  Trees more stressed, as from drought and poor planting sites, are more susceptible to this borer. White-barked species have more of the chemical rhododendrol, which is a borer attractant.
   
Since birch sap is active or “runs” in spring, wait until summer to prune them or they will “bleed” sap. This sap has been a traditional drink in northern Europe and similar cold climates of the world.  In Alaska and some areas it is boiled, similar to maple sap, to make a similarly used syrup. The many and varied birch uses around the world range from twigs used in saunas, to leaves used in teas, to wood used in furniture and bark for containers and canoes.
   
The European birch is one of the most popular and commonly seen, due in part to its lovely white bark with black fissures, and bright yellow fall leaves.  There are several cultivars, including ‘Purpurea’ with reddish-purple leaves, or ‘Crispa’ with finely and deeply cut leaves. This birch, however, is susceptible to the birch borer, heat and drought.
   
Similar to the European in appearance, only with non-dropping branches, is the Paper or Canoe birch (B. paypyrifera).  Its white bark tends to peel off (“exfoliate”) in strips, which can be attractive and led to its name.  Native Americans of the northeastern U.S. used the bark of this native tree to line canoes.  This birch, too, doesn’t tolerate heat, drought, and pollution in cities. 
   
Paper birch is quick-growing, short-lived, and with weak branches that can snap under winter ice loads.  They seem to get birch borers less than the European birch, and leaf miners less than the Gray birch.  The cultivar Prairie Dream is resistant to the borer.  They’re good wildlife plants, hosting larvae for luna moths, and attracting many birds such as yellow-bellied sapsuckers, black-capped chickadees, tree sparrows, redpolls, and pine siskins.
   
Gray birch (B. populifolia) is another native birch tree, having whitish-gray and non-peeling bark.  This tree with multiple trunks is similar otherwise to the paper birch, with which it can be confused.  It is similar, too, in problems and cultural limitations. Yet it will tolerate dry and sandy soils better than some other birches, and is fairly resistant to borers.
   
Sweet or Black birch (B. lenta) is yet another native, only with dark brown, cherry-like bark and golden yellow fall leaves—some of the best fall color of birches.  It may not grow well near paved areas and buildings that reflect heat, nor in dry and sandy soils.  It will grow in part shade, and is resistant to the birch borer.  The bark contains an oil with wintergreen scent, apparent when you scratch the bark.  This fragrant bark was used in the past to flavor beer and relieve many illnesses, from colds to cancer.  The wood has been used by furniture makers.
   
A native birch more commonly found in forests than for sale is the yellow birch (B. alleghaniensis).  It has attractive copper-colored bark that peels off in sheets, as well as yellow fall leaves.  It, too, dislikes dry and sandy soils, and hot sites, but has good borer resistance.
   
Perhaps the most popular birch seen now in landscapes is the river birch (B. nigra), and in particular the cultivar Heritage or ‘Cully’.  One attraction is the reddish cinnamon to salmon bark, which shreds and peels in curls when trees are young, with less peeling as the trees age.  Leaves are bright green in spring, glossy dark green in summer, yellow in fall, and are doubly cut along the edges.  You can find these birches with single or multiple trunks. 
   
River birch will tolerate heat quite well, some shade (at least four to six hours of direct sun), and wet sites as well as some drought, although in longer dry periods it will shed some leaves.  It is immune to the birch borer, and perhaps the most trouble-free birch overall.
   
There are other birch species less commonly found, there being 30 to 60 worldwide.  There are other cultivars, too, primarily of the river and European white birches.   Plant birches in proper sites, and keep them healthy, and they should grow for 40 to 50 years or more.  Otherwise, they may decline and die before 20 years old, especially the white-barked ones.


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