It is important to provide additional winter protection for the Maples, Locust, Linden, Apple,
Crabapple, and Plum species. Until these trees mature and
develop a thicker-insulating bark, they remain vulnerable to sun
scald and frost cracks.
Sun scald is a tree injury that can result in
cracks and splits on the trunk. It occurs in the winter usually on the
south or west side of the trunk. The damage takes place when the cells
in the living tissue beneath the bark break dormancy on warm, sunny days
and then rupture and die when night temperatures drop below freezing.
The tree is injured when enough cells in a given area are killed. The
following spring these dead areas will appear discolored and sunken. In
time the bark killed by sun-scald will split and peel. These areas also
provide entry points for insects and diseases.
To reduce or eliminate sun scald injury, wrap the trunks of
susceptible trees each fall with tree wrap paper. Do this for one or two
seasons until the bark begins to roughen. Remove each spring so as not
to provide a home for insects. Tree trunks can also be treated with
white latex paint, wrapped with burlap, or a light colored tree guard.
One of the most common reasons for cracks and splits
on tree trunks is cold temperature. These are called frost cracks and are
caused when the inner and outer wood in the tree's trunk expands and
contracts at different rates when temperatures change. This happens when
winter temperatures plummet below zero especially after a sunny day when a
tree's trunk has
warmed by the sun. The different expansion rates between the inner and
outer wood can cause such a strain on the trunk that a crack develops.
Frost cracks occur suddenly, can be several feet long and are often
accompanied by a loud rifle shot sound. They often originate at a point
where the trunk has been physically injured in the past. Isolated
trees and trees growing on poorly drained soils are particularly prone to
Frost cracks often close during summer only to reopen in succeeding
winters. They do not seriously hurt trees although they provide openings
where certain disease organisms may enter, particularly if the tree is
in a weakened condition. Frost cracks are also ideal hiding places for
insects which can cause further damage to the weakened tree.
Wrapping the trunks of newly planted trees with tree wrap paper in
the fall may help avoid frost cracks. As mentioned above, be sure and
remove it each spring so as not to provide homes for insects. If damage
occurs, simply remove any loose bark hanging along the edges of the
crack using a sharp knife to give a clean cut. There is no need to paint
the wound with tree paint.*
* Reference- Missouri
Botanical Gardens website, see our links page.