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Whitewash tree trunks to prevent winter sun-scald
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December 23, 2005
CORVALLIS, Ore. – Whitewashing tree trunks is an old-fashioned, but effective method to prevent sun-scald of tree bark from bright winter sunshine. Cold weather during the past two out of three winters has caused bark damage on fruit trees and landscape trees, both in eastern and western Oregon.
“Sun-scald of tree bark occurs when tree bark is exposed to warm daytime temperatures and sunlight during cool weather,” explained Ross Penhallegon, horticulturist with the Oregon State University Extension Service.
The warmth coaxes the light-exposed tissues out of dormancy, causing them to need enough moisture to support active growth. At the same time, the cold temperatures around the shady sections of the tree, including the roots, remain too cold for those parts of the tree to break dormancy. These cooler, dormant tissues are unable to take up the moisture needed by the active tissues.
“As a result, the warmed tissues of the tree dehydrate and die, causing the tree to be dead on its south side by the time spring arrives,” said Penhallegon.
In western Oregon, during mostly cloudy winters, home orchardists sometimes whitewash their trunks purely for aesthetic reasons.
“Rows of whitewashed trees make an orchard look clean, neat and attractive,” he said.
To whitewash a tree trunk or two in your home landscape or orchard, Penhallegon recommends the following mixture for whitewash: Dissolve three pounds of table salt in 12 quarts of water. Then, slowly add and stir in 10 pounds of hydrated lime.
Or an alternate whitewash mixture can be made with 50 percent exterior white latex paint and 50 percent water, he said.
For painting rough bark, make the first coat a little thinner than the recipes above, by using more water in the mixture. The second coat can be of the consistency of the above recommended mixtures. Let the first coat dry before applying the second. Stir the mixture frequently as you paint.
Another alternative is to wrap the trunks with paper, plastic or cloth. These materials will help to protect the bark.
Source: Ross Penhallegon