Gardening: Winter sun causes young trees to develop cracks in bark

For the News-DemocratOctober 18, 2013 

Q. I have noticed on three of my trees that there is a split in the bark on the south or southwestern side which extends for 9 inches on each of them. The bark appears to be growing over where these splits have occurred. I don't remember doing anything to these trees but just noticed them this fall. What could this be? Can I save the trees or should I cut them down and start over? They are about 6 to 8 inches in diameter. We just moved into this house this past year.

-- R.C. of Belleville

A. The locations of the splits on the bark of three trees all in the same direction seem to indicate a condition termed "frost cracks." In winter, when the angle of the sun is lower and shines on young trees with smooth bark, the bark heats up and expands. At night, when the temperature drops quite a bit, the bark cools very quickly and contracts. This happens over many nights and a crack develops and expands.

To prevent this, wrap the trunk with tree wrap. This wrap is brown and wrinkled, usually with an asphalt material between the two layers of wrap. Start the wrap at the base of the tree and slightly overlap the wrap as you work your way up the trunk. At the top, hold the wrap in place with two complete circles of masking tape. If you forget to remove the masking tape next spring, the tape will loosen over time and will not girdle the bark of the tree.

The good thing that you describe is that the bark is beginning to callus around the split and there is growth over the injured area. This fall, after all the leaves have fallen off the tree, add a tree fertilizer. Looking upward, notice how far out the branches extend from the trunk. This outer area of leaves is referred to the drip edge or the area where rain falls off the tree similar to an umbrella. Apply this tree fertilizer in granular form. Do not use tree fertilizer spikes as the roots will grow to the concentrated areas of fertilizer causing competition with the tree's roots. You want the tree's roots spread uniformly underground to hold the tree as good anchors.

Apply about 3 pounds of fertilizer for each inch of diameter of the trunk as measured 4 1/2 feet above the ground. It will not hurt the grass but the grass may grow a little faster in this area next spring.

Once the tree has developed course bark, you can stop wrapping the tree. The tree wrap will also prevent borers an insect pests from boring into the conductive tissues of xylem and phloem, which move water upward in the tree and bring manufactured sugars to other parts of the tree.

If you notice some of the bark being pushed outward and appearing to be dead, you can remove it carefully with a sharp knife or pruners but do not make any cuts into the callus material.

You should not have to replace these young trees. Any decay should be minimal and should not develop into the new outer bark tissue.

Charles Giedeman is a local contributing writer. Send your gardening questions to Lifestyle Editor Pat Kuhl, Belleville News-Democrat, P.O. Box 427, 120 S. Illinois St., Belleville, IL 62222-0427. Or email to

Do it now

FALL CLEANING: Clean up the flower and vegetable beds and compost the old material unless you notice a lot of diseased leaves on the plants that you are removing.

COVER CROP: You can prepare the beds with a cover crop of annual ryegrass vetch, or clover to help encourage good tilth and organic fertilizer in these beds next spring.

SOIL TEST: This is a good time.

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