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.
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 (see image to left below), 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.