Winter’s severe cold weather takes its toll on all of
us and trees are no exception.
Frost cracks are thought to occur when trees differentially
heat up and cool down in winter.
This uneven cooling and heating sets up stress inside of
trees and the result is a frost crack.
Heating and quick cooling can also cause the phenomenon of
sun scald.
Sunscald and frost cracks normally occur on the south and
south west sides of young trees.
In the winter the sun is at a low angle and shines on the
bark of trees warming the surface as the day progresses. Large swings in
temperature occur as the sun sets and the bark rapidly cools.
The stress caused by differential heating can cause the tree
to split outright, as is the case with frost cracks or just damage the living
cells in the cambium layer and result in sun scald . The cambium is a layer of
growing and dividing cells just under the bark but above the hard wood of the
tree. When the cambium is damaged the bark will crack and peel off leaving dead
regions of trunk.
Once a frost crack occurs and the tree is split there is no
chance it will rejoin and “heal”.
The crack itself allows fungi and other pathogens to enter
in to the heartwood of the tree and can lead to decay. While this does lead to
a reduction in strength it does not always lead to failure, immediately or in
the near future. Trees with this condition can live for many years and be
effective elements in a landscape. If the tree is close to structures or areas
where people sit it should be inspected regularly and well maintained. The tree
responds by trying to grow over the crack, however the growth itself pushes the
crack wider. In the end the tree may fail prematurely but not unexpectedly if
your Arborist has pointed this out.
Sun scald damages large areas of cambium in newly planted
trees and they should be considered for replacement.
Wrapping newly planted trees with white paper and protecting
the trunks of trees with understory plantings are two solutions that can be
used for new plantings. Be sure to remove paper wrappings once the threat of
frost has passed. Once trees are established you may not have to wrap them.
Over pruning, or lifting of young trees will contribute to damage from the sun
so use caution when removing the lower branches from young trees. If you have a
planting project in mind or suspect you have sun scald or frost cracks contact
you I.S.A. Certified Arborist.
I.S.A Certified Arborists are constantly updated on the
latest planting and pruning methods backed up by scientific research on tree
wound response.
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