Every garden is a thing of beauty in the growing seasons – spring bulbs, summer flowers and fall foliage all carry on with extravagance. But winter is coming, so the colorful garden superstars will soon be retiring for the year. Fortunately, that’s when one of the most overlooked features, tree bark, comes out for its season in the spotlight. From warty to smooth, peeling to furrowed, brown to gray to red to white, tree bark brings a terrific variety to its role as arboreal armor.
As attractive as it is, bark also has a serious purpose: protecting the tender rings of living cells from drying winds, heat, cold, insects and animals. Just under this outer bark is an inner bark layer, known as phloem, which transports sugars, manufactured by photosynthesis in the leaves, down to the roots for storage. Next in is the cambium layer, where new wood is produced, followed by the sapwood, or xylem. This layer moves water and nutrients from the roots back up to the leaves.
Finally, at the center of the tree, comes the heartwood, a central core of inactive xylem.
Without these layers intact, the tree can’t grow. That’s why a tree can be killed so easily by girdling – carving a strip around the entire tree – which can happen easily from weed whackers, hungry animals or improper bracing of a newly planted sapling.
Trees develop their characteristic barks as the trunk circumference grows. The dead outer bark can’t grow, and so it gives way. Beech bark (Fagus spp.) is flexible, so it stretches and expands.
Black locust (Robinia pseudoacacia) develops deep ridges and fissures, while black cherry (Prunus serotina) forms flat plates. Bark characteristics will change on the same tree over time, too.
The bark of a young red oak (Quercus rubra) is smooth and shiny, later becoming rough and corrugated. European white birch (Betula pendula) goes through several stages, from shiny brown bark to white, and, finally, showing dark gray fissures painted with white lines of leftover white adolescent bark.
Sweet cherry (Prunus avium) develops barkless horizontal rings called lenticels along the length of the trunk that act like breathing pores.
Some trees, like paperbark maple (Acer griseum), sport bark that peels away in papery layers, while others, such as shagbark hickory (Carya ovata), show strips of bark that curl at each end like rocking-chair runners.
Let Mother Nature handle stripping these trees in her own time; peeling the bark by hand will injure the tree. Of course, color is the most striking characteristic of bark.
The scintillating emerald vertical ribs of the striped maple (Acer pensylvanicum) look like shimmering green ribbon candy, while the randomly black spotted, creamy coat of a quaking aspen (Populus tremuloides) takes on the look of Army winter camouflage.
For interesting peeling and flaking bark, try these favorites (Fort Wayne is in Zone 6a):
American sycamore (Platanus occidentalis); Zones 5-9.
Japanese stewartia (Stewartia pseudocamellia); Zones 5-8.
London planetree (Plantanus x acerifolia); Zones 3-9.
River birch (Betula nigra); Zones 4-9.
These trees feature bark with bright colors and compelling textures:
American beech (Fagus grandifolia); Zones 4-8.
European beech (Fagus sylvatica); Zones 4-7.
Flatspine prickly ash (Zanthoxylum simulans); Zones 6-9.
Paper birch (Betula papyrifera); Zones 2-7.
Ironwood (Carpinus caroliniana); Zones 3-9.
Quaking aspen (Populus tremuloides); Zones 1-8.
Variety is the spice of life, and including deciduous trees with interesting barks makes for a garden with true four-season charm. Their greatest contribution is often found in winter, when barks’ varying hues and textures add life and much-needed visual appeal in a potentially otherwise drab winter setting.