Monday, November 24, 2014

Winter Bark Damage

Fruit trees spend a good portion of their existence in dormancy. This is a time for the tree to rest and prepare for the right spring conditions to wake them up so they can preform their annual ritual of blossom, growth and fruit production. There are several outside factors that can disrupt a fruit tree's routine, leaving you with marginal success at harvest time. One problem that will be discussed in this blog post is winter bark damage.

Most fruit trees have dark colored bark. In the winter months they display their contrast well against the white snow. This dark bark can be a real weakness in some climates. When the temperatures are low and the sun is shining bright, fruit trees absorb the warm rays like a lazy cat in the window. When the dark bark of the tree is exposed to direct sun light, the temperature of the tree's outer layer becomes much warmer than the outside air, the same way asphalt will warm and melt snow in the winter even if the temperatures do not go above freezing. This temperature change causes the bark to expand during the day. When the frigid temperatures of night cool the bark again, it constricts back to it's former size. Bark is able to withstand a certain degree of expansion and contraction, but this freezing and thawing on a daily basis will often cause permanent damage to your fruit tree. 

You will know that your tree is suffering from this condition if you see deep cracks in the bark that ooze sap in the spring. Younger trees will heal and recover quickly from this type of damage, but older trees will have their bark completely separate from the wood. This condition is typically present on the southwest sides of a tree's trunk or on the top of older mature branches that are exposed to full sun during the winter months.Whole branches that are dependent on water and nutrient transport on this side of the tree may die off completely and will need to be removed.

Winter Bark Damage on an Old Peach Tree
There are two ways to prevent this condition on your fruit trees. You will need to either paint the trunk of your tree white or wrap the trunk with a light colored tree wrap. The light color of the paint or wrap will minimize the temperature change preventing expansion and contraction and will protect your tree from winter bark damage. I recommend wrapping your trees in the fall and removing the wrap in the spring. That way you are not left with an unsightly white painted trunk in your garden. 

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