Trees are an important part of our landscapes. They add beauty, they improve the environment, they stabilize the soil and prevent erosion and they can play an important role in energy saving.
However, they also may present a risk to the public’s health, safety and welfare. This story will address a number of issues that can cause a tree to turn from a friend to a foe.
One has to remember trees are living organisms and assessing tree problems is an ongoing process. Recognizing issues before they cause harm and dealing with them promptly can save big in the future.
It also must be remembered that, as living organisms, no tree is risk free. All trees will fail under the proper circumstances.
It is important to recognize as early as possible the common tree problems that create risk to people, structures, and other targets of value. The targets may be on your own or even adjacent property.
Tree problems may be initially divided into two broad categories: abiotic and biotic. Abiotic factors are non-living conditions or things, i.e. weather, that influences an organism.
Biotic factors may be defined as any living component that affects another organism. Many abiotic factors originate due to the actions of people.
Mechanical injury to trees frequently results in increased risk. The risk may increase over time due to the introduction of biotic factors such as bacteria and fungi.
Mechanical injury often is the result of the use of heavy equipment during construction. Some mechanical injury results from well-intentioned landscape maintenance such as weed eating, mowing too low, or mowing too close to trees.
Wrapped wires around trees or limbs eventually will cause girdling if not removed. Something as simple as using a wire to hang a plant or birdfeeder can, if not removed in time, girdle and kill a tree limb.
Fires are another abiotic hazard. Many of our forest species, like pines, benefit from periodic burns. But something as simple as a fire pit, barbeque grill or a burning pile of leaves can harm many of our landscape plants.
The top few inches of soil beneath the fire can reach several hundred degrees, killing roots. Fires too near a tree trunk can destroy the plant’s vascular system and be a point of entry for biotic factors like fungi and bacteria. The leaves and limbs in the tree canopy above a fire can be injured or ignited by rising heat.
Roots are vital living parts of plants. Approximately fifty percent of the total mass of a tree is underground. It depends on the species, but that is a good rule of thumb.
Eighty percent or more of the roots of a tree are in the top ten to 12 inches of soil. The roots of a tree have been shown to extend out from the trunk three or more times the height of the tree.
These roots perform the important functions of water and nutrient uptake and structural support. Injury or destruction to roots has serious effects on the above-ground portion of the tree.
Something as simple as driving a piece of heavy equipment across the same ground two to three times is enough to begin compacting the soil and destroying roots. Parking a car or pickup truck in the same location repeatedly may result in compaction and root death.
Digging a trench as shallow as one foot potentially destroys nearly all of a tree’s roots from beyond the trench away from the trunk. The closer the trench is to the tree, the greater the amount of root destruction. Installing or maintaining a landscape irrigation system, house water line or sewer line are all potential causes of root damage.
Roots are adapted to growing at a certain depth. Adding or removing soil from around a tree can seriously impact root health.
The loss of root support makes a tree more susceptible to wind damage. Root death results in reduced water and nutrient uptake leading to stress and possible plant death.
Cultural practices, however well intentioned, may increase tree risk if improperly performed. Tree health may be affected by improper planting.
Planting too deep or too shallow can impact establishment. As previously stated, roots are adapted to growing at a certain depth. Trees should be planted at the same depth as they were growing in the plant nursery.
The lack of proper establishment may not be immediately apparent. A properly planted tree will establish so it can live without excessive supplemental care within one year.
An improperly planted tree may never become established. Once established, regular, routine maintenance is important for good plant health.
Other root issues which may impact root zone development include girdling or circling roots, frequently the result of remaining in a container past the time it should have been moved to a larger container.
Achieving a healthy, established tree starts long before planting. It starts in the nursery, making proper plant selection important.
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