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.
Birch in park. Credit: geographic.org.uk |
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.
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