Sun scald, sometimes called southwest injury, is a common problem that affects trees, especially in climates with bright winter sunlight and freezing temperatures. Fruit trees, young trees, and those with thin bark, such as maple, honey locust, linden, beech, dogwood, and mountain ash, can be especially susceptible. Maples, in particular, are highly vulnerable to sun scald due to their thin bark and sensitivity to environmental stressors.
Learning how to recognize, prevent, and manage sun scald is crucial for tree health, whether you have newly planted trees or a mature landscape.
What Is Sun Scald?
In the northern hemisphere, sun scald most often appears on the south or southwest side of a tree’s trunk during the winter months. This area is exposed to direct sunlight on cold, clear days, which causes the bark tissue and underlying plant cells in the trunk to become active. The bark is heated by the sun, leading to increased cellular activity. Sun scald occurs when these temperature fluctuations damage the tissue.
When winter temperatures drop suddenly at night or when the sun sets, the rapid cooling can kill the plant tissue, resulting in dead bark and discolored bark. Affected areas may appear sunken, dry, or later become an elongated canker.
Sun scald is not limited to winter; summer sun scald can occur during high temperatures and intense sunlight in the summer, particularly when trees are stressed by moisture depletion.
Which Trees Are at Risk for Sun Scald?
Thin-barked trees are most vulnerable, especially those species with smooth bark. Some trees highly susceptible to sun scald include:
- Maple
- Honey locust
- Linden
- Beech
- Dogwood
- Mountain ash
- Fruit trees (apple, pear, peach, cherry, plum)
- Newly planted and young trees (their bark hasn’t developed protective layers yet)
Older trees with thicker bark are less likely to be affected, but sun scald damage can still occur if their canopies are pruned up high, exposing the lower trunk to direct sun.
How to Identify Sun Scald Damage
Check for the following signs on the southwest side or the south part of the tree trunk, especially in late winter, early spring, or the next spring after injury:
Discolored Bark That Is Pale, Gray, or White
This discoloration is often one of the earliest visible signs of sun scald damage. It indicates that the bark tissue has been affected by temperature fluctuations and cell death. Over time, this area may become more pronounced and spread if left untreated.
Sunken or Elongated Cankers on the Bark
These cankers represent areas where the bark has died and begun to collapse inward, creating a sunken appearance. They can differ in size and usually stretch lengthwise along the bark’s grain. This damage can compromise the tree’s protective barrier, making it more vulnerable to further injury.
Peeling or Splitting Bark Revealing Dead Tissue
As bark tissue dies, it typically starts to crack and peel off the trunk or branches, revealing the dead tissue underneath. This peeling exposes the underlying dead tissue, which can dry out and become brittle. Such damage can provide entry points for insects and diseases, further threatening the tree’s health.
Decay and Insect Infestation in Damaged Areas
Once the protective bark is compromised, decay-causing fungi and wood-boring insects can invade the exposed tissues. This can lead to further deterioration of the affected branches or trunk sections. Detecting these issues early and taking prompt action is essential to minimizing further harm.
Weak or Stunted New Growth Near Injury
Sun scald damage can disrupt the flow of nutrients and water within the tree, leading to poor growth near the injury site. New shoots may appear smaller, weaker, or fail to develop properly. This stunted growth is a sign that the tree is struggling to recover from the damage.
If you notice signs of sun scald like discolored or peeling bark on your trees, don’t delay in addressing the issue. Our certified arborists at ArborCraft Tree Service are experts in diagnosing and treating sun scald, offering customized prevention and care to keep your trees healthy and vibrant year-round.
How to Prevent Sun Scald on Trees
Step 1: Use Tree Wraps
Start by wrapping the vulnerable trunks of your trees with tree wrap or applying white latex paint from fall through spring. These coverings reflect sunlight and heat, helping to reduce harmful temperature fluctuations in the bark. Make sure to take off the wraps once the risk period is over to prevent trapped moisture, which can harm the tree.
Step 2: Prudent Planting and Pruning
When planting new trees, choose locations that offer some natural shade during winter to protect the lower trunk. Avoid pruning away lower branches on young or thin-barked trees, as these branches provide essential shade and reduce sun exposure. This careful approach helps shield the bark from direct sunlight and temperature stress.
Step 3: Maintain Tree Health
Keep your trees well-watered during dry spells to minimize moisture stress, which can weaken bark tissue. Apply mulch at the base to help conserve soil moisture, but be sure to leave a few inches of space to prevent rotting. Also, be careful when using lawn equipment near trees to avoid damaging the bark, which serves as a protective layer.
Step 4: Species Selection
Choose tree species that are naturally less prone to sun scald or have thicker bark when planting in areas where this problem is common. Choosing the right species can significantly reduce the chances of sun scald damage in your landscape. This proactive step helps your trees better handle temperature extremes.
How to Treat and Manage Sun Scald Damage
Once sun scald damage has occurred, timely and appropriate management can help your tree recover and reduce the risk of further complications. Here are key steps to effectively treat and manage sun scald damage:
- Remove Loose Bark Carefully. Gently peel away any loose or dead bark around the damaged area to prevent pests and diseases from entering. Avoid cutting into healthy bark, as this can cause additional injury to the tree.
- Avoid Using Wound Dressings or Paints. Do not apply pruning paint or any other wound dressings. These products will trap moisture inside, basically rotting whatever you were trying to save, even more. Research shows that natural healing without these products is typically more effective.
- Monitor for Insect and Disease Infestation. Regularly inspect the damaged area for signs of insect activity or fungal infections, which can take advantage of weakened bark. A vulnerable spot may fall prey to such things, and early detection helps avoid further disaster for the tree.
- Promote Overall Tree Health. Support your tree’s recovery by maintaining proper watering, mulching, and fertilization practices throughout the growing season. Healthy trees are better equipped to compartmentalize damage and grow new tissue.
- Protect the Tree From Further Stress. Avoid additional wounds from lawn equipment or heavy pruning near the damaged area. Reducing stressors helps the tree focus energy on healing and new growth.
- Consider Professional Assessment. For severe or extensive sun scald damage, consult an arborist who can evaluate the tree’s condition and recommend specialized care. Professional advice may include targeted treatments or structural pruning to improve tree stability.
Act Now to Prevent Tree Damage: Call ArborCraft Tree Service
Sun scald is more than a cosmetic problem; it can lead to long-term health declines in your trees. By recognizing risks, employing wraps or white paint, selecting strategic planting sites, and keeping trees healthy, you can effectively prevent sun scald.
If you’re concerned about sun scald or have noticed symptoms such as discolored or peeling bark on your trees, don’t wait until minor damage becomes a major problem. At ArborCraft Tree Service, our certified arborists have the experience and knowledge to diagnose and treat sun scald and other tree health issues accurately. We offer tailored prevention strategies, professional assessments, and ongoing care to keep your landscape beautiful and your trees thriving year-round.
Contact us today to schedule a consultation and let our team help your trees flourish for years to come!