Gardening Help FAQs

Here are answers to some of the most common questions we receive about garden plants. You will find concise information on general gardening techniques as well as plant selection and care. For detailed information on specific plant pests and problems refer to our Common Garden Pests and Problems page.

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Horticulture Questions and Answers

What causes cracks and splits in tree trunks?

Cracks and splits in tree trunks are fairly common and may occur for various reasons. They are usually not a significant threat to the tree. Typically there's not much you can do about them once they occur.

One of the most common reasons for cracks and splits on tree trunks is cold temperature. These are called frost cracks and are caused when the inner and outer wood in the tree's trunk expands and contracts at different rates when temperatures change. This happens when winter temperatures plummet below zero especially after a sunny day when a tree's trunk has been warmed by the sun. The different expansion rates between the inner and outer wood can cause such a strain on the trunk that a crack develops. Frost cracks occur suddenly, can be several feet long and are often accompanied by a loud rifle shot sound. They often originate at a point where the trunk has been physically injured in the past. Maples and sycamores are the most prone to frost cracks. Apples, ornamental crabapple, ash, beech, horse chestnut and tulip tree are also susceptible. Isolated trees and trees growing on poorly drained soils are particularly prone to frost cracks.

Frost cracks often close during summer only to reopen in succeeding winters. They do not seriously hurt trees although they provide openings where certain disease organisms may enter, particularly if the tree is in a weakened condition. Frost cracks are also ideal hiding places for insects like earwigs, although the insects do not harm the tree directly.

Frost cracks are not preventable. Wrapping the trunks of newly planted trees with tree wrap paper in the fall may help. If you do wrap, be sure and remove it each spring so as not to provide homes for insects. Apple growers whitewash the trunks of apple trees to prevent frost cracks and other winter injury problems. Homeowners can use white latex paint, but some gardeners may find this unattractive in a landscape setting. The best way to prevent a secondary effect due to frost cracks is to promote good growth and prevent injury to the trunk throughout the tree's life.

If damage occurs, simply remove any loose bark hanging along the edges of the crack using a sharp knife to give a clean cut. There is no need to paint the wound with tree paint. For large, serious cracks a professional arborists can bolt the cracks shut with a technique called lip bolting.

Sun scald is another form of injury that can result in cracks and splits. It occurs in the winter usually on the south or west side of the trunks and branches. The damage takes place when the cells in the living tissue beneath the bark break dormancy on warm, sunny days and then rupture and die when night temperatures drop below freezing at night. The tree is injured when enough cells in a given area are killed. The following spring these dead areas will appear discolored and sunken. In time the bark killed by sun- scald will split and peel. These areas also provide entry points for insects and diseases.

Young thin bark trees are most susceptible to sun scald injury. These include beech, honey locust, lindens, mountain ash and sugar maples. Heavy pruning on neglected trees can also expose sections of bark that were previously protected from the sun's direct rays. This can predispose these areas to sun scald injury. To reduce or eliminate sun scald injury, wrap the trunks of susceptible trees each fall with tree wrap paper. Do this for one or two seasons until the bark begins to roughen. Remove each spring so as not to provide a home for insects. Tree trunks can also be treated with white latex paint.