Tree bark, the outermost layer of a tree, sometimes appears to shed or fall off. While this might seem alarming, it is not always a sign of a problem. Understanding the reasons behind bark loss can help distinguish between natural processes and causes for concern.
The Role of Bark
Tree bark serves as a protective covering, similar to skin for animals, safeguarding the tree’s internal structures. This tough outer layer defends against physical damage, pests, and diseases, preventing microorganisms and insects from entering the softer inner tissues.
Beyond protection, bark regulates the tree’s internal environment. It insulates against extreme temperatures and minimizes water loss. The inner bark, known as phloem, transports sugars produced during photosynthesis from the leaves to other parts of the tree, supporting growth and development.
Natural Bark Shedding
One common reason for bark shedding is the tree’s natural growth process. As a tree grows in girth, its trunk expands, and the older, less flexible outer bark may crack and peel away to accommodate the new growth underneath. The inner bark continuously renews itself, with dead cells becoming part of the protective outer bark.
Aging also contributes to natural bark shedding, as older bark layers may flake or exfoliate over time. Many tree species exhibit distinctive and predictable bark shedding patterns as a normal part of their life cycle.
For instance, sycamores (Platanus species) are well-known for their exfoliating bark, which peels off in irregular patches to reveal lighter, often mottled inner bark. Birches (Betula species) often have papery bark that peels horizontally in thin strips. Eucalyptus trees (Eucalyptus species) frequently shed long strips of bark, exposing smooth, colorful new bark underneath.
Causes of Abnormal Bark Loss
Bark can also fall off due to various stressors or problems that compromise the tree’s health. Pest infestations, particularly from insects like borers, can cause significant bark damage. These insects tunnel into the cambium layer, which is the growth tissue just beneath the bark, disrupting the flow of water and nutrients and causing the bark to loosen and detach. Evidence of insect activity, such as small holes, sawdust-like frass, or exit holes, often accompanies this type of bark loss.
Diseases, often caused by fungi or bacteria, can also lead to bark shedding. Canker diseases, for example, create sunken, discolored areas on the bark that can eventually girdle a branch or trunk, cutting off nutrient transport and causing the bark to die and fall away. Environmental stressors can further weaken bark integrity. Frost cracks, which are vertical splits in the bark, occur when rapid temperature drops cause the outer bark and wood to contract at different rates.
Sunscald, common on young trees or those with thin bark, happens when intense sunlight heats the bark, causing tissue damage that leads to cracking and peeling. Drought stress can also cause bark to crack and shed as the tree attempts to conserve moisture and experiences overall decline. Physical injuries, such as those from lawnmowers, construction equipment, or even animal damage, can directly wound the bark, making it vulnerable to pests and diseases and potentially leading to localized bark loss.
Distinguishing Normal from Concerning Bark Loss
Differentiating between natural shedding and problematic bark loss involves observing several indicators. When bark sheds normally, the exposed wood underneath typically appears healthy, often lighter in color, and smooth or with a consistent texture. In contrast, concerning bark loss often reveals discolored, decayed, or insect-damaged wood underneath. This damaged wood might appear dark, wet, or have visible tunnels or fungal growth.
The pattern of shedding also provides clues. Natural shedding often occurs uniformly around the trunk or in characteristic patterns specific to the tree species. This shedding tends to be widespread but consistent. Problematic bark loss, however, usually appears in localized patches, vertical cracks, or cankers, indicating a specific area of damage or infection.
Assessing the tree’s overall health is another important step. A tree experiencing natural bark shedding will generally have healthy, vibrant foliage and no signs of wilting or discoloration. If bark loss is accompanied by symptoms like wilting leaves, yellowing or browning foliage, branch dieback, or fungal conks on the trunk, it suggests a more serious underlying issue. Considering the context, such as recent severe weather events, nearby construction, or recent physical damage, can also help determine the cause of bark loss.
Addressing Bark Loss Concerns
For bark shedding that appears to be a natural process, simply monitoring the tree’s health and appearance is usually sufficient. There is no need for intervention if the tree otherwise looks vigorous and healthy.
If the bark loss exhibits concerning signs, such as discolored wood, localized damage, or accompanying symptoms of decline, it is advisable to contact a certified arborist. Arborists can accurately diagnose the cause of the bark loss and recommend appropriate treatment options, which may include pest management, disease treatment, or structural support. It is important to avoid applying homemade remedies or attempting to treat the tree without professional guidance, as improper treatments can further harm the tree. Practicing good tree care, such as ensuring proper watering, applying mulch to regulate soil temperature and moisture, and protecting the trunk from physical damage, can help maintain bark health and prevent many issues.