A predominant feature of trees in the winter landscape is the bark. While bark doesn’t receive much attention most of the year, it is much easier to see in winter without the presence of leaves and can be quite fascinating upon closer inspection.
What is bark and what does it do?
Bark consists of living and dead plant cells present at the periphery of plant stems. Bark is a distinctive characteristic of woody plant species and can be as unique to a tree as its leaves. Bark has similar functions for most trees. The primary role of bark is protecting the inner living cells from fire, predation, and other threats. Some species of trees, such as bur oak (Quercus macrocarpa) have bark that is particularly resistant to fire. Other trees have bark with thorns (honeylocust or Gleditsia triacanthos) that protect the tree from animals.
In addition to protecting trees, bark is utilized for other purposes. In the rainforest, epiphytic plants, like orchids, anchor their roots into the bark of trees. Many animals and insects use bark as hiding places or habitats. Humans have used bark in various ways for centuries. Bark has been used to make canoes, baskets, clothing, medicines, and dyes. The popular spice cinnamon is obtained from the bark of several tree species from the genus Cinnamomum. The cork oak is the primary source of wine bottle stoppers and other uses. Today, bark is widely used by homeowners for mulching landscape beds and paths
The diversity of bark.
The color and texture of bark is as diverse as the various tree species themselves. Rainbow eucalyptus (a tropical tree) is noted for having almost all colors in its bark. There are also several tree species with colorful and attractive bark for Midwestern landscapes.
Sycamore (Platanus occidentalis) bark consists of patches of green, gray, white, and tan that are randomly pieced together like a scrappy quilt. In winter, the strikingly light-colored bark on sycamores can be seen from a considerable distance in urban forests and natural areas.
A similar patchwork of colors can also be found on the bark of older lacebark pines (Pinus bungeana), or stewartias (Stewartia koreana). While it may require some effort to find these smaller trees for sale in your area, they make great additions to the landscape.
Walking in the woods, it is easy to recognize the flaky, gray/taupe strips of shagbark hickory (Carya ovata) and white oak (Quecus alba). These Iowa natives are excellent, long-lived landscape trees for sites with plenty of space.
Another popular landscape tree with peeling bark is the river birch (Betula nigra). The river birch has peeling cream, tan, or pale peach colored bark. Trees are often sold with several trunks, creating a distinctive appearance in the landscape. River birches perform best in moist, slightly acidic soils.
A smaller tree with peeling bark is the paperbark maple (Acer griseum). It has smooth, cinnamon-colored bark that peels off in paper-sized sheets. Paperbark maple does best in sheltered locations in central and southern Iowa.
Several trees, such as beech (Fagus sylvatica) and cherry (Prunus) are noted for their smooth bark. Both trees perform best in protected locations in the southern half of Iowa.
Japanese tree lilac (Syringa reticulata) is a more cold hardy selection suitable for all of Iowa. It has smooth reddish-brown bark. It is also smaller than many of the trees listed above, therefore, it can be planted closer to buildings. Other options for smooth gray bark, are hornbeam (Carpinus species) and serviceberry (Amelanchier species).
Black walnut (Juglans nigra) and Kentucky coffeetree (Gymnocladus dioicus) display coarse, deeply furrowed bark in the winter months. The gray ridges and black furrows are rugged looking and provide a stark textural contrast in the winter landscape.
These are just a few of the trees that I see and enjoy while walking on the Iowa State University campus. While you are out and about this winter season, glance at a few of the trees you pass. The patterns, textures, and colors of bark are worthy of a second look.