Young Trees Should Be Protected From Sun Scald: Ask a Master Gardener
By Tulsa World, Okla.
Dec. 1–The Master Gardener: Vija Sevier
Q. I recently planted a red maple in my yard. The nurseryman suggested I wrap the trunk of the tree this winter. I have mulched it; is the wrapping really necessary?
A. Young trees fresh from the protection of the nursery environment have thin bark, which is susceptible to damage from the cold. How this damage occurs is an interesting and unique process.
With the onset of the cold weather, trees go into dormancy. The living cells in the cambium layer stop growing and adjustments are somehow made to tolerate freezing. Then, on a winter’s day following a very cold night, the sun comes out and warms up the part of the trunk facing the sun.
This side of the stem may reach temperatures twice or more the opposite side of the trunk. The living cells that are warmed might come out of dormancy and lose their protection from the cold because they think spring has arrived.
A recurrence of freezing at night then kills those activated cambium layer cells. This produces an elongated split in the bark or even a large open wound that is an entry point for diseases in the next growing season.
Because
the damage most commonly occurs on the sun-facing side of the tree, the process is often called “southwest injury” or “sun scald.”
The trees most susceptible are maples, ashes, birch, linden, fruit trees and others. The Oklahoma redbud is among those susceptible.
As mentioned, this is most likely to occur in newly planted trees during the first two years after planting.
Prevention consists of shading the trunk from the sun. There are lightcolored paper and plastic trunk wrap materials sold for this purpose. Burlap or similar material that is loose and offers shade also may be used.
Do not use duct tape or similar binding tapes. Anything binding on the trunk can kill the tree.
The wraps should be applied to the trunk now and removed in March at the start of the growing season. Do this for two years. Don’t forget to remove in spring — these wraps may harbor insects and disease in the summer.
Other things that might help: Don’t prune off the lower branches on the tree for the first two years, because they offer trunk shade.
Also, keep the tree well watered in the winter and fertilize either in fall or spring.
The Tulsa Master Gardeners are trained volunteers who help provide information and support to home gardeners and the community.
For more, go to www.tulsaworld.com/mastergardener.
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If you have a garden-related question you would like the Master Gardeners to answer in a future column, call Kim Brown at 581-8474 or email her at kim.brown@tulsaworld.com.
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Copyright (c) 2007, Tulsa World, Okla.
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