Yes, trees get sunburn too. After reaching 105° this weekend, we thought we’d give some tips on how to protect your young (and older) trees from the intense heat.
Ever wonder why the trunks of citrus trees are painted white? The reflective paint protects the sensitive bark from the scorching effects of the strong sun. Like citrus trees, desert adapted trees also need protection from the sun, particularly young trees.
Signs of sunburn can take a little while to appear so it’s important to monitor your trees. A first sign of sun damage to a desert adapted tree like a Palo Verde is uneven bark color, from yellow to pale green (pictured below). For trees with gray bark, a brown discoloration can occur and later the bark can crack or peel away from the tree (pictured right). While sun is needed to produce food for the plant, too much sun will burn plant tissue on leaf and bark surfaces. Trees with broad leafs, like Mesquites, have tubes which lay underneath the bark and transport energy from the leaves down to the roots. When the bark is sunburned these tubes are often affected and the tree is no longer able to carry food to the roots.
To prevent sunburn, it is important to select the proper tree type for the climate. Properly selected desert adapted trees have smaller leaves that release less water and tissues that are better suited for our intense sun. Proper placement of the tree is equally important, as trees planted in west and south facing locations receive the intense late afternoon sunlight. Refrain from planting trees in the heat of the summer or make sure to protect the newly planted trees.
Another preventive measure against sunburn is to allow branches that grow along the lower part of the trunk--called watersprouts--to keep growing for at least two years before pruning or removing them. The lower branches not only encourage strong trunk growth, they also shade interior branches and protect the trunk from sunburn. Properly prune your tree to prevent from removing too much of the canopy which exposes tree bark to large amounts of sunlight. Improper irrigation or watering techniques can also lead to leaf loss and further sun exposure.
If tree sunburn does occur it is important to address it as untreated sunburn can lead to borer infestation and damage to the tree. To help your trees heal, allow all branches to grow without pruning in order to increase the shade coverage over the exposed bark. Wrap shade cloth or tree wrap around the sunburned area and regularly monitor it.
Just as we protect our skin from the intense Arizona sun, take preventative measures with your trees to protect them against sunburn.
http://xtremehorticulture.blogspot.com/2011/09/palo-verde-dont-like-butch-hair-cuts.html (photo image 1)
http://www.gardeningknowhow.com/plant-problems/environmental/sunscald-on-plants.htm (phone image 2)
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