Sunscald and Sunburn in Plants

Identifying Sun Damage
There are two main kinds of sun damage in the plant world: sunburn (also called leaf scorch), which affects the foliage, and sunscald, which affects the bark. Sunburn occurs in plants for like it does in people – too much light and heat, with increased risk when dehydrated. But unlike us, the sunburned plants don’t immediately turn pink. The damage can take longer to become apparent, and results in yellow or brown foliage. If the damage progresses, the leaves die off starting in the areas between the leaf veins.
Sunblock for Plants
When preparing to plant any new landscaping in sunny areas, prevent sun damage by selecting native plants and plants that are adapted to the light conditions where you will be growing them. If you will be transplanting established plants, avoid moving them into significantly more sun than they are used to. Mulching around plants can help conserve water, reduce reflective light around plants, and reduce the soil temperature to ease heat stress. Apply a 3 to 6 inch layer of wood chips, straw, cocoa hulls, or other biodegradable material around the root zone of the plants. Leave a few inches space from the plant stem or tree trunk to discourage pests and prevent diseases such as crown rot.
Put up some shade fabric over shorter plants, or wrap the trunk of at-risk trees, when they are getting too much sunlight. Different types of plants need different amounts of shade. Don’t overdo it or you’ll end up with pale foliage and spindly shoots from inadequate sunlight! For your trees, you can apply a coat of white indoor latex paint diluted with equal parts water to any areas that are not receiving enough shade from the tree’s canopy. Young trees and trees with thin bark such as sugar maples are at the most risk of sunscald and would benefit from a yearly coat of paint until their canopy develops. Proper pruning also helps in sunscald prevention: never prune more than 20% of the canopy in one year to maintain sufficient shade for the bark. Tree wraps provide an easy alternative to paint for young trees. Simply wrap the over-exposed bark in Spiral Tree Guards to provide shade to those areas. Tree wraps also provide additional protection against some insect and rodent damage.
As the mercury rises and the days get longer, it’s time to protect your plants and yourself from the sun!
Do you have any advice for treating sunscald once it’s on the tree?
Janet, once your tree has it you can’t reverse it, but you can wrap it to prevent further damage. You can use the spiral tree guards or follow the directions for making up the latex paint (not approved by organic certifiers).