Frost cracks and sun scald
Have you ever wondered why your tree may have a long vertical scar going up the entire side of the trunk? Or perhaps you have looked at the same tree on a bitter cold winter day and noticed that it has split open and has a wide gaping crack? These are frost cracks and it is a very common occurrence.
It is believed that the sun warms the surface of the tree on the south and west facing side of trees. On very cold nights when the sun falls and the temps drop well below freezing causes wood tissue to contract, however the inner layers of wood are better insulated and slower to contract than the outside layers. This causes pressure to build within the wood until a loud popping sound results in a frost crack. Oftentimes when the internal pressure has evened out and stabilized the crack appears to close up again. The tree will then grow callous tissue around the wound over the course of the following summer.
For the most part the wounds are typically only a couple inches deep but I have measured some trees to have very deep cracks of 6” or greater. Trees for the most part are able to heal themselves by growing callus tissue similar to how our own skin heals itself by growing a scar. Unfortunately the resulting scar is now a weakened area that will always be susceptible to opening again in extreme temperature fluctuations. The resulting wounds can also be an entryway for decay causing organisms such as Eutypella Canker in Maple.
Sun scald is another common problem in winter on young trees with paper thin bark. This is also caused by rapid temperature changes and can result in the bark dying and falling off on the side of the trunk leaving a large wound that can take years to heal.
It is believed that wrapping the tree trunk in fall and removing the wrap the following spring can help prevent sun scald on young trees. Brown paper tree wrap has been used for years and is okay however white plastic tree guards are better because the white color will reflect sunlight. Additionally the plastic is a good barrier to prevent injury from deer rubbing their antlers on the bark and from rodents such as rabbits, mice and voles who eat tree bark in winter when other food sources are scarce.
It’s recommended to put tree wrap or tree guards on trees for the first few years until the bark has thickened and developed texture which will have better resistance against sun scald and animal damage.
As always if you see something that doesn’t look right or if you have questions about the maintenance and care of your trees give us a call and have one of our ISA certified arborists take a look, it’s what we are here for.