Diagnosing Sunburn

September 18, 2003

Although they are not encountered as frequently as water stress or aeration deficit, this disorder is not uncommon and should not be overlooked.

Sunburn is injury to above ground plant parts (leaves, bark, flowers, and fruit) caused by excessive exposure to solar radiation. Injury results when tissue becomes dehydrated. Similar to what we experience at the beach, pool or working in the yard.


Sunburn may cause leaf discoloration and necrosis. The epidermis may appear glazed, turning a silver or reddish-brown color. Sunburned bark initially appears discolored (often a reddish-brown) and then becomes dry. Cracking and peeling is typical, and damage is usually most severe on the south or southwest side of branches and trunks.

Although sunburn is most common in summer, it can occur at any time of year, even in winter. Injury is most severe during periods of high temperatures. Plants that tolerate full sun conditions may be damaged when temperatures reach a critical level. Tree trunks in closely spaced container nursery rows are frequently shaded, when planted sun-exposed bark is prone to sunburn. Trees that have been excessively pruned have no leaves. These leaves have protected the trunk and limb wood for many years. Loss of this protection can cause severe damage and/or death, sometimes it occurs immediately or it can take a period of years.

Deciduous trees may sustain sunburn injury during the winter months. When branches previously protected by leaves are exposed to direct sun, bark tissues may be sunburned. Similarly, when branches or trees shading other trees are removed, sunburn may result. This can be particularly severe on young trees, thin barked species, and water stressed trees.

Santa Ynez Valley Tree has provided you with an opportunity to make an educated decision about tree CARE. Take a few minutes and browse our web site. In a short time you, like us at SYV Tree will know the destructive power of greed and ignorance. Call us. We know what your tree needs!

Santa Ynez Valley Tree Care
P.O. Box 1147, Santa Ynez, California 93460

(805) 688-5580

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