Adventures in Gardening: Might Your Tree Crack?

by David Soper

This winter has been particularly tough on plants in much of America. It is too soon to really assess the damage, but here is something you can check for now.

You might examine the trunks of your younger trees or those with smooth barks. You're looking for frost cracks. A frost crack is a long, deep, narrow crack running up and down the trunk. They usually appear on the south or southwest side of the tree but can appear anywhere.

These cracks are caused when the sun warms the trunk in winter (the south exposure is usually warmest) causing the tissue to expand. When clouds or nearby buildings block the sunshine, the temperature of the trunk quickly drops to the temperature of the air around it. The cold air causes the trunk to shrink. And, since the outside and the inside don't shrink at the same speed something has to give, thus creating the problem.

Once a crack happens, you don't have many options. Some people have had limited success by fertilizing heavily. This helps the tree grow more quickly therefore closing the crack more rapidly.

Aside from appearances, frost cracks also can allow rots or canker diseases to invade the tree.

There are a couple of prevention strategies. You can reduce the risk of frost cracks by wrapping younger trees with paper tree wrap. As unlikely as it sounds, the paper does work to disperse the heat of the sun. Be sure to start wrapping at ground level. Continue to wrap up to the first main branches.

If some of your younger trees are fruit trees, you might consider painting the trunks with white latex paint. This is very big in Europe. The theory here is that the white surface reflects the sunlight away from the tree and therefore reduces overheating.

David Soper, The Garden Guy, writes and lectures on gardening topics. Check out his books at

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