Question
QUESTION: Hi, I live in central Alberta Canada and in cold hardi zone 3a. I have planted a weeping crab, mayday, and princess kay plum last summer and fall and started noticing very small striations running vertically and only on one side of the trunk. They were between 24" and 30" up from ground level, with multiple scratches within a 4" height and 1" width.Over time they get progressively worse. The bark curls away and the scratches are more prevalent. My first thought was a cat was using it as a scratching post but then started thinking about my planting. Each hole had bone meal and was mixed with the surrounding soil. The princess kay died with these striations that had worsened over time 3 months after planting. The weeping caragana is still going this year but is not budding all that well and is looking sickly. The mayday had died this spring and it was planted last summer. The location of these trees are in town by a urban treed area with loads of nature around but on the flip side these trees are in peoples yards in a high population area that have all sorts of pets. I have asked local nurseries about the problem and have showed them pictures and they don't have an answer. All these trees have the same exact "striations". Could these be frost cracks, animal, planting ....ahhh. The pictures I have are on my phone and have yet learned how to put them on the computer so will send or post asap.I need to know. It's buggin the heck out of me. Thanks

ANSWER: Sounds like sunscald. Cracks in the Trunk, Sun Scald.

Sunscald is a form of injury to the trunk of many landscape trees. Often called southwest injury, it usually occurs on the southwest side of young trees. As the sun shines on the tree trunk, cells within the tree break dormancy and become active. When the sun sets and temperatures get colder, the active cells are killed. This injury may appear as sunken and discolored bark. By spring, the bark may crack and fall off in areas along the trunk. Dead tissue is revealed under the cracked bark. The injury is most severe on thin-barked deciduous trees, such as honey locusts, fruit trees, ashes, oaks, maples, lindens, and willows. Sunscald occurs on warm winter days.

To prevent sunscald, the trunks of susceptible trees can be covered with tree wrap. This is put on in the fall and must be removed in March to prevent girdling and possible insect damage. Until the bark has thickened on young trees, they may need to be wrapped yearly. Be sure to scout for insects and carefully remove any bark not attached to the trunk of the tree.

Another product that can be used on the trunk is tree paint. White latex paint is often used in orchards to help prevent splitting and cracking on fruit trees. The paint will help reflect light and heat from the tree trunk. Due to aesthetic reasons, most homeowners are not interested in using tree paints. Both tree paints and wraps can be found at local garden centers and nurseries.

The last injury causing cracks is due to temperature fluctuations during the winter. These cracks are often called frost cracks. They are caused by expansion and contraction of a tree抯 trunk. Extreme temperature changes can set this up.  As temperatures change quickly, bark from trees will crack. Frost cracks are not serious as long as they are kept clean to prevent disease and insects. Wrapping trees in the fall may help prevent further occurrence. Be sure to remove all wraps in the spring to prevent disease and insects from invading the tree.






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QUESTION: I guess one thing that I forgot to mention was that where the markings are. It's the north west side. The princess kay plum was sheltered by a fence (3' away), the weeping caragana was in a front yard facing the south but markings on the n/w side and the mayday same...n/w side.?

Answer
I still think it is winter injury. Bark splitting appears as loose bark in various areas on the trunk. As the bark exfoliates from dead tissue on the trunk, a frost canker can form. The canker may initially appear as a darkened, moist area. Bark splitting can cause structural damage and reduce the plant抯 ability to transport nutrients and water. This can cause the death of the entire plant.

Frost cracks on the trunks of woody plants can occur  when plants are exposed to extremely cold temperatures. A frost crack is a long, deep, narrow crevice running up and down the trunk of a tree. As temperatures cool down, the temperature of the trunk drops quickly and the trunk contracts and may split. Frost cracks can be on different sides of the trunk.