Frost cracks in trees.
Tree trunks very often experience vertical fractures caused by low temperatures. It is then, when on sunny winter days the trunk heats up strongly from the sunny side. The increase in temperature increases the volume of the heated part of the trunk. Rapid night-time drops in temperature result in a rapid cooling of the trunk surface and a peripheral shrinkage of the wood mass. Internal wood mass, still having a higher temperature and greater volume, creates stress. Such a stress is obviously the greatest on the most heated side, and this is also where the trunk fractures most often. It is accompanied by a strong bang, or rather a crack (hence the saying "crackling winters"). Slots like this, depending on the thickness of the trunk and the quality of the wood, they may be 0.5-3 cm wide. In the case of uniform heating of the entire trunk, its middle part usually breaks, although often the crack runs along its entire length. Slots like this, after the temperature of the trunk equalizes, usually close, without disturbing the tree static. Damaged cambium at the fracture site produces healing tissue on both sides, which, fusing together, closes the gap. As a result, characteristic scars appear at the site of the fracture (drawing).
Drawing. Frost crack of the trunk and the method of depositing the healing tissue on the edges of the fissure.
In many cases, however, especially in these trunks, which are not evenly loaded (asymmetrical crowns) the gap caused by the fracture does not close (drawing).
Drawing. Removal of a broken trunk with the use of steel bars and the method of shaping the places of seating for the washers and the edge of the slot; this shaping facilitates the deposition of the healing tissue.
Often, such fractures also enlarge as a result of the action of various forces transmitted to the trunk, causing bending, twisting, etc.. The considerable width of the remaining fissures and the movements of their edges make it impossible to close the fissure with even intensively healing tissue. Under such conditions, wood becomes infected. An infested tree can decompose quite quickly, and it is favored by rainwater flowing down the branches and trunk getting into the wound. Therefore, each crack requires disinfection as quickly as possible. Because the gap is narrow, thus, access to the wood surface is limited, therefore, decontamination by spraying an appropriate agent with a sprayer is more effective than by lubrication. If the gap created is deep and does not close, then it is recommended to tie tightening the parted edges, namely the use of steel bars passing through the trunk. When assuming several bars, they should not be placed in the same straight line, thus preventing the trunk from breaking when twisted. The edges of the crack should be cut at an angle of 45 ° by 2-3 cm inward. This makes it easier to care for the wound until it is healed and to deposit the healing tissue. Before twisting the bindings, the joint should be dry and generously smeared with orchard tar, so that after twisting all free spaces would be filled with it.
Cracks left with their edges open for several years and not cared for can be a great threat to the trunk, for the decay of wood is progressing in them. Very often "rolls" of healing tissue, the fractures formed at the edges of such a crack are in contact with each other, giving the appearance of healing the wound, however, a rift remains inside. The relatively high humidity maintained there favors the decomposition of the wood. It is fairly easy to check this by inserting a thick wire through the gap between the heaps of healing tissue. By the time, when decomposition of the wood has not yet occurred, treatment of such places is carried out in a different way. Due to the expected infection, and even the initial wood decay, the stump fracture cannot be closed as in the case shown in the figure above, because it would foster the progress of decay. Such a place must be left open, and even widened to facilitate disinfection and protection against water soaking and to facilitate drying. Healing tissue produced at the edges should be cut. The degree of crack widening may depend on the required accessibility of the crack's internal surfaces or the condition of the wood, which need to be removed. The edges of the joint should be cut at an angle of 45 °; this will facilitate the deposition of healing tissue. If leaving and widening the gap violates the required static properties of the tree or may cause further cracking of the trunk, then it should be mechanically reinforced (drawing).
Drawing. A method of treating an open and neglected frost crack: a - fracture with damaged wood and healing tissue produced at the edges; b - the formed interior and edges of the damage site and the method of applying a tie that strengthens the trunk.
Such reinforcement differs from that used for pressing the wood at the fracture site, that the twisted rods, thanks to the inserted pipe sections, do not bring the plane of the slot closer while twisting. The reinforcement can also be made of several or more bars. It is of great importance in trees exposed to strong winds. Susceptibility to frost cracks is not the same among species. The trees are very susceptible to trunks breaking: chestnut trees, ash trees, clones, elms and plane trees. Preventing cracks is quite difficult. Natural protection that causes slight shading of the trunk are numerous branches in the lower part of the crown and branches of trees growing nearby. Fully exposed trunks are most vulnerable. The easiest way to protect them is to protect them from the sun's rays, e.g.. fabric, roofing felt etc.. An effective way is to paint the trunk in white, similarly to fruit farming. However, this method cannot be used in parks, on the streets, etc..