Shedding, peeling, or splitting bark on trees in the landscape can be a concerning sight.
While not always a cause for concern, these symptoms can be harmful to the tree for many important reasons:
- The bark protects trees (and their important water and food-conducting tissues located just beneath the bark) from animals and mechanical injury.
- The inner bark is involved in the transport of mineral elements and the products of photosynthesis.
- Without bark, important regenerative tissues and water-conducting elements that reside just below the bark could desiccate or suffer mechanical injury.
Understanding what is causing the bark loss is an important first step to preventing further damage.
Normal Growth & Development | A Characteristic of the Tree | Extreme Weather Conditions | Lightning | Mechanical Damage | Sunscald | Frost Cracking | Smooth Patch | Insects & Diseases | Management | More Information
Normal Growth and Development
Split or cracked bark on some trees is a completely normal development. The bark of most young trees is smooth and thin. As the tree grows, the bark layer thickens, and the outermost tissue eventually dies. Continued growth pushes the bark outward, causing the outer layers to crack. On some trees, the outer dead layers peel and drop off, revealing the inner layers of bark.
Bark cracking from normal growth and development does not require any management. It is identified from other sources of bark damage by the appearance of the tissue inside the crack. Inside the crack is healthy developing bark and no exposed heartwood.
A Characteristic of the Tree
Shedding or peeling bark is characteristic of trees such as sycamore, redbud, silver maple, shagbark hickory, birch, and Scotch pine. For example, the grayish-brown bark on a large sycamore tree flakes off in irregular blotches, revealing a cream or whitish gray inner bark. In some years, trees may lose larger than normal amounts of bark. Dry conditions in summer and fall and/or cold winter conditions may loosen more bark than normal, leading to the heavy loss of bark. Despite the loss of large amounts of outer bark, there is no cause for concern if the trees appear otherwise healthy. On older redbuds, the outer bark on the trunk often falls off, revealing orangish-brown inner bark. Long, thin strips of bark may also come off large silver maples.
Extreme Weather Conditions
Rapid fluctuations in either air temperature or soil moisture can potentially cause the loss of bark. Extremes (high or low) in air temperature and/or soil moisture may also lead to peeling, shedding, or splitting bark. These reasons, however, are not yet well understood.
Lightning
Trees struck by lightning can develop long vertical strips of bark to be blown or loosened from the tree as the lightning strike follows the water-conducting vessels just under the bark down the tree, exploding the bark. An arborist should evaluate trees impacted by a lightning strike. Often, these trees have internal damage that may make the tree unsafe.
Mechanical Damage
Mechanical damage from animals like squirrels, as well as errant lawnmowers or weed trimmers, can cause the bark to loosen, peel, or strip away.
In fall, bucks rub their antlers on trees to remove the dried velvet from their antlers and to mark their territory. This rubbing removes the thin layer of bark on small trees and can seriously damage or destroy them as it disrupts the water and nutrient-conducting tissues in the tree. Young trees with flexible trunks and thin, smooth bark are most likely to be damaged. Learn more about preventing this damage from this article: How to Prevent Trees and Shrubs from Animal Damage Over Winter.
Sunscald
Cracking and peeling of bark on the south or southwest sides of young fruit trees, red maples, and lindens is frequently observed in the landscape. Often attributed to sunscald, the damaged bark comes off completely down to the wood. The loss of bark will reduce the vigor and health of the tree and possibly shorten its life. If the trunk eventually becomes completely girdled, the tree will die. Learn more about managing sunscald in this article: Winter Damage on Trees
Frost Cracking
Vertical cracks in a tree's bark and wood may appear on its trunk or branches in winter. Frost cracks result from an imperfection in the wood that tends to open and close on an annual basis. Low temperatures seem to trigger the reopening, but the origins of the crack are usually traced to an injury or some other injurious event earlier in the life of the tree. There is little management that can be done once cracks have occurred. As the weather warms, the cracks close again. This seasonal opening and closing is stressful and may be an entry point for decay fungi and insects. Sometimes, these wounds may develop a raised area created from callus tissue developing in an attempt to close over the wound.
Smooth Patch
Certain saprophytic fungi (those that live on dead organic matter) decompose the rough, dead outer bark of trees. This results in smooth, light, grayish patches adjacent to the normal, rough bark. Small patches may expand slowly over time, merging to form smooth grayish areas several feet in length. Aleurodiscus oakesii is one of the fungal species that can cause smooth patch and may occur on trees such as American elm, sugar maple, and various oaks.
Some of these fungi produce whitish fruiting structures visible on the bark, which sometimes causes them to be mistaken for serious wood decay fungi. These smooth patch fungi, however, do not cause cankers or internal decay. They cause no known harm to the tree.
Smooth patch is also referred to as white patch or bark patch.
Insect Pests and Diseases are Rarely the Primary Problem
Often, holes from feeding woodpeckers, fungi fruiting bodies, crawling insects, or other disease-causing agents are found near or under peeling or splitting bark. While these issues are not healthy for the tree, they are typically a secondary invader of an area already damaged by some other cause. Understanding and addressing the primary reason for the damage will help prevent further damage from things like butt and root rot, carpenter ants, and other insects and diseases.
Management of Shedding and Peeling Bark
Treating exposed areas of wood with wound dressings or paints is not advised or recommended. Similarly, taping or tacking bark pieces or strips back in place is rarely a successful repair strategy unless it can be done immediately after the injurious event occurs. The loose bark can be carefully removed, being careful not to cause further damage to the surrounding intact bark. Proper and timely supplemental irrigation remains our best recourse and remedy for young trees that have suffered injury to important bark and vascular tissues.
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