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BARK SPLITTING ON TREES
Introduction
Bark
splitting can occur in response to various environmental factors at
different times of the year. Splits can occur on the trunk of the tree as
well as on branches. Trees which are most susceptible to this type of
injury are those which are thin-barked, such as certain fruit trees.
Newly-planted trees or young trees are more prone to bark-splitting. Bark
splits are not likely to be fatal to trees, although they will, in some
cases, allow entry of disease organisms which can cause decay. Through
proper treatment to encourage the natural callusing process, a tree should
be able to close most splits.
There is no single reason for bark
splitting on trees. During late winter and early spring, severe cold
followed by rapid thawing can result in splits referred to as "frost
cracks". These frost cracks can actually start from a wound inflicted
earlier in the tree's development. Sometimes the crack may remain in the
internal wood, but frosts can cause the crack to expand and split the
bark. Excessively late growth in the fall stimulated by warm temperatures,
high humidity, and high nitrogen levels can increase susceptibility of
trees to frost cracking.
Fluctuating growth conditions may also
cause splitting of bark. Dry weather (which slows growth) followed by wet
or ideal growth conditions may cause an excessive or vigorous amount of
growth leading to splits in the bark.
Symptoms
Figure 1: Bark Split
on Kwanzan Cherry |
Figure 2: Bark Tracing to remove
split |
Sunscald, especially in winter months, can cause bark
injury to thin-barked or young trees. Although an exact split may not be
seen immediately, the outer layer of bark will peel away from the affected
area in the summer following the winter damage. Sunscald injuries to tree
limbs can be minimized by avoiding heavy pruning of trees which have dense
canopies. Gradual thinning of limbs over a period of years is preferable,
particularly on thin-barked trees. Newly planted trees may be protected
from sunscald by wrapping main trunks with tree wrap.
As mentioned
before, certain trees are more susceptible to splits than others. The
trees on which we receive the most inquiries concerning splits are Kwanzan
cherry (Figure 1), maple, and fruit trees. Any newly-planted tree, especially of a
thin-barked species, is a candidate for bark-splitting if it is not cared
for properly. Be particularly careful to avoid fertilizing the trees late
in the growing season, as this may promote new growth and predispose the
tissue to winter injuries (including bark splitting). Autumn fertilization
following leaf drop and dormancy should not lead to this problem.
Management
Strategies
When a split
occurs on a tree, what should you do? In recent years, quite a bit of
research has been done on closure of tree wounds. These investigations
have indicated that tree wound paints are of little value in helping a
tree to callus over. For this reason, do not paint or try to seal a split
with paint or tar. Tracing the bark around the split can be very helpful
in aiding wound healing (Figure
2). With a sharp knife,
starting from one end of the split, trace around one side of the wound,
about 1/2 to 1 inch back from the split bark. Stop at the other end and do
the same procedure on the opposite side of the split. Knives should be
sterilized between cuts by dipping them for several minutes in a 1:10
bleach:water solution or a 70% alcohol solution to avoid contaminating the
cuts. Carefully remove the bark from inside the traced area. You should
now have a bare area resembling the diagram in Figure 2.
Remember to leave this untreated. A tree growing with good vigor usually
calluses over quickest. Encourage vigor in the tree with yearly spring
fertilizer applications -- and be sure to provide adequate irrigation in
hot, dry weather. Bark splits will often close over completely leaving a
slight ridge in the trunk where callus tissue has been produced.
Last updated, KLS, 8/99
Source: The Plant Disease Diagnostic Clinic at Cornell
University.
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