Wednesday, August 16, 2017  

Bark: The Outer Beauty of Trees


Structurally gardens progress from the relatively minor size of perennials and annuals to shrubs and then trees. To create a pleasing garden you need to configure the spaces to step up from the lawn height to the height of the towering tallest of the trees. Landscape designers often refer to this as bringing the scale of the landscape down to human size. Trees are an important part of that process. The English refer to all outside spaces as the “garden” and not just a space within the yard that is planted by humans.

In the spring the brilliant green of the leaves and some flowers are the showy parts. In summer the leaves provide cooling shade and in the fall they shine with autumnal shades of burgundy, gold and brown. When the perennials are dormant and the annuals have died and are in the compost pile, you have the opportunity to view the structure of the trees without their leaves. The trunks of the trees offer up an abundance of texture and interest. They “back up” or create an elegant backdrop for your view.

Bark is the outside layer of the stems and roots of woody plants. This layer is the dead tissue of the tree. The inner bark or peridum is the living tissue. The cambium inside the peridum carries the nutrients and water to the rest of the tree so that it can grow. The bark protects the inner layers against exterior damage from storms or during construction when all sorts of mechanical intruders come too close to the trees and cause abrasion and outright wounds. Sometimes trees are wounded during storms when other trees fall upon them or from the wind. Tree guides, left on for too long or applied too tightly, can cause damage as well. Allowing for the growth of the tree is sometimes forgotten. Fences with barbed wire strung too close to a tree trunk and signs nailed into trees can cause weakened areas in the trunk and access for insects and disease. Other times trees are injured by deer foraging or rubbing their antlers against the trunks to assist them in removing the velvet on their antlers. Sometimes insect damage can injure or even kill a tree and incorrectly used insecticides and pollution can do immense damage and even cause death.

So how can you tell if the bark on trees is peeling because of disease or insect damage or has architectural interest? Why do they peel? Bark peels like our skin does, shedding its outer layers and replacing it with inner newer layers. During this process the inner layers are often exhibited and the color may be intensified as with sycamores and crape myrtles. The healthy process of peeling bark often lends itself to attractive interest in the landscape. Unhealthy peeling differs from that. When bark peels and exposes newer bark that is healthy that is a normal process of rejuvenation. When bark peels exposing bare wood, damaged areas or mats of fungus it is because of insect damage or disease. Peeling of bark on the south or south west side of trees with bare wood exposed can be caused by sunscald or frost damage. Some varieties of trees are bred for their attractive peeling bark and add another dimension to the landscape.

Bark is used for shingle siding, wall coverings, spices, tanbark for tannin, resin, latex and some hallucinatory chemicals as well as cork. Cork, a secondary tissue, is valued because it is impermeable to gasses and water. It is used in flooring for these qualities as well as sound reduction. Bark is also used to make canoes, cloth, ropes, landscape mulch and in map making.

The care of trees has many horticultural focuses, and some of these ideas have changed over time. It was believed that wounds on tree trunks needed to be “sealed” with paint or a tar-based substance to assist in the healing process. So following pruning or damage the substance was applied and allowed to stay in place. Over time this belief has changed. Now it is believed that leaving a wound alone and not covering it with a paint-like material allows the tree to heal without harboring bacteria or insects that may do greater damage.

It is truly a miracle to see trees that have been damaged during some time in their lives and continue to grow and thrive despite it. Wander through the woods and notice. Sometimes you see a tree bent over or growing suddenly halfway up its trunk in a totally different direction. You have to wonder what happened that caused that change and be amazed at its ability to recover and thrive. Burls or large irregular structures on trees are caused by a fungus. These are treasured by wood workers and make attractive bowls.

When the leaves are down we have an entirely different view of our trees. Their trunks and limbs are more visible. It is amazing how beautiful they can be. The texture of a tree can reveal many things about it. Some are smooth as with properly pruned Crape myrtles, while cherry trees sport shiny bark with slim horizontal lines. Gold birches have beautiful smooth golden bark that peals and adds great interest to the landscape. Dawn redwoods generally have arrow-straight main trunks but with a hint of red. Redwoods are deciduous losing their needle-like leaves in the winter and showing off their arrow-straight reddened trunks. Maples can run the gamut of brown to green stripes or have beautiful red pealing bark. Paper birches have showy white bark while river birches can be golden and brown adding immense texture to your garden.

And the sycamores! Watch for them when their blotchy gray and white bark stands out even more against the clear blue sky. Consider strongly planting tree varieties for their bark interest. Trees grown for their colorful or naturally shedding bark include: silver maple, birch, sycamore, redbud, shagbark hickory and Scotch pine.

The trunks of trees can be augmented with paint. Yes, paint. When viewing the entrance to a nursery I noticed the white trunks of several small trees and inquired. I was informed and it was confirmed by our forester that painting the trunks and branches of trees with latex paint does not harm them. Think of the possibilities. Picture the white trunks and curving branches of a delicate dogwood in the spring when white flowers are on each branch. Then the leaves emerge and add contrast. In the fall the leaves turn a brilliant red. Spectacular! In wintertime the leaves are down and the structure of the whitened branches and trunk add a new dimension to your landscape. They are truly beautiful when it snows.

Trees can easily be identified at all times of the year. Take a naked tree walk with the Native Plant Society or your forester. Look for the large scales on the trunks of loblolly pines and how it sets itself apart from the striated bark of the black gum. Look for the impressive shagbark hickory and feel the large peals on its sides. Try to learn to identify a tree without cheating and looking at the leaves gathered around its trunk. Compare the shape of a spreading oak to the oval shape of a Bradford pear. Test yourself while riding as a passenger in a car and guess what variety of tree you are seeing.

The wounds of trees can tell many stories. They also can provide shelter for small animals. Woodpeckers not only obtain food in the form of insects from the bark of trees but often shelter within them. Look for the oval holes of the pileated woodpecker. The bark of trees continues to provide shelter and nourishment even when its life is through. Notice the abundant growth of mosses, lichens, mushrooms and even tiny ferns on a fallen “nurse” tree which decays and as it is used up returns to the earth as humus to fertilize the forest.

Bark adds texture, color and interest to every view. It protects and embellishes the beauty of trees. It grows from a sapling with a smooth exterior and at maturity provides us with the opportunity to feel, look and enjoy its interesting qualities. As Anne Morrow Lindbergh wrote in Gift from the Sea when comparing seashells to life stages of women, the oyster is like middle age with a roughened exterior and a polished and mother-of-pearl interior. This is also true with the bark of trees as they roughen over time harboring a fine wood interior, meanwhile providing shade and housing and certainly visual interest. It is so wonderful to be able to walk in the woods, to view and enjoy wonderful trees of many varieties and touch them and feel their bark.