Bark, the outer layer of trees, protects them from environmental elements, pests, and diseases. Similar to human skin, bark can undergo exfoliation, a natural process where portions peel or shed. For many species, this shedding is a normal part of their growth and development, revealing distinct patterns and colors beneath the surface.
Trees Known for Shedding Bark
The American sycamore is well-known for its mottled bark that flakes off in large, irregular pieces. This process exposes patches of lighter, creamy white, green, and brown inner bark, giving the trunk a camouflage-like appearance. Sycamores shed bark throughout the year, with increased shedding during hot summer months or after wind events.
Birch trees, particularly river birch and paperbark birch, exhibit prominent bark peeling. River birch has cinnamon-colored bark that peels in papery strips, often revealing lighter layers underneath. Paperbark birch has pure white bark that sheds annually, initially appearing yellow before maturing to white. This shedding can be most pronounced for the first few decades of the tree’s life.
Eucalyptus species are famed for their dramatic bark shedding. As the outer bark dries and peels, it unveils a vibrant mosaic of colors, including creamy whites, pale grays, oranges, reds, and even purples. The way eucalyptus bark sheds can vary, coming off in flakes, curls, or long strips depending on the specific variety.
The London plane tree, a hybrid often found in urban environments, features olive green to gray bark that peels in large, scaly plates. This shedding exposes a creamy, smooth bark beneath, contributing to its distinctive camouflage pattern. Similarly, the paperbark maple has papery, cinnamon-colored bark that peels in thin sheets, revealing a vibrant orange-red inner layer.
Crepe myrtle trees are noted for their smooth, two-toned bark that sheds, creating color variations on their trunks. Other trees like the shagbark hickory display a shaggy, peeling bark.
Reasons for Bark Shedding
Bark shedding serves several important functions for a tree’s health and survival. One primary reason is to accommodate growth; as the trunk expands, the rigid outer bark cannot stretch. Shedding old, dead outer layers allows new, living bark to form and prevents cracking from internal pressure, enabling the tree to continue growing and maintaining its structural integrity.
Shedding bark can also rid trees of accumulated organisms like pests, fungi, lichens, and mosses that colonize the outer surface. By shedding these layers, the tree reduces the risk of infestations or disease. For instance, eucalyptus trees shed bark to remove harmful oils and resins, in addition to deterring pests.
Environmental adaptations also play a role. Some trees shed bark to cope with specific conditions, such as high temperatures. In certain species, the newly exposed inner bark may even be capable of photosynthesis, contributing to the tree’s energy production, especially when leaves are sparse. This process helps trees maintain health and vigor in their habitats.
When Shedding Bark Signals a Problem
While bark shedding is often natural, certain signs can indicate an underlying issue. If bark falls off in unusually large patches, or exposes bare wood instead of healthy, fresh bark, it may signal a problem. Discolored, mushy, or soft inner wood beneath the peeling bark is also a concern.
Cankers, which are localized sunken or discolored lesions on the bark, can point to fungal or bacterial infections. These cankers might ooze sap or moisture, and the inner bark may appear black or dead. Signs of insect activity, such as sawdust around the base of the tree, small holes in the bark, or winding tunnels, suggest a pest infestation.
Symptoms of tree stress accompanying bark loss include wilting leaves, discolored foliage, or dead branches. If shedding occurs after extreme weather events like sudden temperature drops or heat waves, it could be a sign of weather-related stress. If any concerning signs are observed, especially if bark damage covers more than 40% of the tree’s circumference, consult a certified arborist.