Tree bark serves as the outermost protective layer of a tree’s trunk and branches. It performs several vital functions. While seeing a tree shed its bark might initially cause concern, it is often a normal process for many tree species.
The Purpose and Layers of Tree Bark
Tree bark acts as a protective shield for the living tissues from environmental threats and physical damage. Beyond protection, bark also plays a role in transporting nutrients and sugars throughout the tree.
The bark is composed of several layers. The innermost layer, the phloem or inner bark, is a living tissue transporting sugars from the leaves to other parts of the tree. Outside the phloem lies the periderm, consisting of cork cambium and cork cells, forming the protective outermost layer.
Natural Reasons Trees Shed Bark
As trees grow, their trunks expand, and the rigid outer bark cannot stretch. This natural expansion causes old bark to crack and peel away. This allows the tree to grow, revealing new bark underneath.
Shedding old bark also serves as a self-cleaning mechanism. It helps remove debris, moss, lichens, and insect infestations. This naturally disposes of potential pests or pathogens, contributing to its health.
Different tree species exhibit unique shedding patterns. Some, like sycamores and maples, have bark that peels in large flakes or sheets, creating a mottled appearance. Others, such as river birches, are known for their distinctive exfoliating or curling bark. These patterns are a healthy part of their life cycle.
External Factors Leading to Bark Loss
While natural shedding is common, bark loss can also signal underlying problems caused by external factors.
Insect pests, like emerald ash borers or bark beetles, bore into the bark layers, disrupting the tree’s vascular system. This damage can cause bark to die and detach as the tree isolates affected areas.
Fungal diseases can attack bark, causing cankers or lesions, weakening the tissue and leading to detachment. Environmental stresses, like drought or extreme temperature fluctuations, can damage bark. Sunscald, caused by intense sun exposure on thin-barked trees, and frost cracks, from rapid temperature drops, can lead to bark splitting and peeling.
Mechanical injuries are a common cause of bark loss. Damage from lawnmowers, string trimmers, vehicles, or construction activities can injure the bark, creating wounds that expose the inner wood. Animals, such as deer or rodents, can strip bark from trees, especially in winter. This damage compromises the tree’s protective barrier.
Recognizing Concerning Bark Issues
Observing the extent and location of bark loss helps determine if it is concerning. Widespread bark loss across the trunk may indicate a serious underlying issue. Localized peeling on one side, especially facing south or west, might suggest sunscald rather than a systemic problem.
Accompanying symptoms provide clues about a tree’s health. Look for signs like discolored or wilting leaves, dying branches, visible cankers, or unusual sap oozing from the bark. Sawdust, small holes, or tunnels on the bark surface could indicate an insect infestation.
Assess the tree’s overall health. A vigorous tree, producing new growth and maintaining healthy foliage, is in good condition, even if shedding bark. However, if the tree appears in decline, with sparse canopy or stunted growth, bark loss could be a symptom of a serious issue. If shedding occurs at an unusual time or with multiple distress signals, consulting a certified arborist is advisable.