Tree Care : Myths and Realities

Photo: Adam Franc

Although trees can usually take care of themselves in rural forests, in urban environments such as your yard or community, trees need protection and appropriate care. These persistent and insidious myths cause many costly and dangerous mistakes in tree care every year. In some cases, some of these myths also cause many trees to be removed prematurely in their life cycle.

Myth : Tree roots break sewer pipes

Tree roots are attracted to sewer lines and will therefore perforate and break these pipes 

  • Reality :

Underground pipes and ageing sewer infrastructure are often at risk of deterioration and breakage over time. Pipe and joint failure can be provoked by environmental changes such as freeze/thaw cycles or ground shifting and heaving. Tree roots are unable to actively pierce or perforate pipes. Small and fibrous tree roots can infiltrate pre-existing cracks in a leaking sewer system. A sewer line leak allows sewage and air to escape into the soil, creating a ratio of air, water and nutrients that are ideal for small feeder roots to grow. Anchor roots at the site of the leak produce very fine, opportunistic feeder roots that can enter the sewer pipe and potentially cause blockages. Without leaks or unsealed pipe joints, tree roots cannot enter sewers nor can they causes blockages. A well maintained sewer system can prevent this type of problem.

Myth: tree roots can damage the foundation of a house

Tree roots can perforate concrete, cause cracks and shift foundations.

  • Reality :

Tree roots cannot survive in hardscapes devoid of water and oxygen, and then cannot perforate concrete. On the contrary, tree roots develop in spaces where sufficient water, oxygen and organic matter are present. Small and fibrous tree roots can be found in leaking pipes and cracks where conditions are humid and air can circulate.

Tree roots are not equipped to detect and seek out water through impervious surfaces. They develop where conditions are favorable to tree growth, specifically where there is a sufficient amount of oxygen and water. Trees do not waste their energy to search for water as root growth is opportunistic. More than 90% of the tree roots are in the first fifty centimeters of soil.

Several factors can cause cracks in a foundation. For example, the use of certain soils for backfilling buildings, the transfer of surface water from roofs and walkways into storm sewers, periods of prolonged drought and the removal of large quantities of soil in locations where trees are present can all contribute to soils to shift, dry out and sometimes shrink. Shrikage can pull away supporting soil from around or beneath a foundation. This leaves room for the foundation to settle unevenly, which can cause cracks.

Myth : when growing, tree roots are able to raise sidewalks to develop

Tree roots are often responsible for raising sidewalks, pavers and walkways

  • Reality :

Sidewalks and hardscapes can shift and heave over time. Several factors can contribute to this such as freeze/thaw cycles, changes in moisture around the foundation and adjacent soils as well as the circulation of heavy vehicles or even poor construction quality. When these surfaces crack and heave, their structural integrity degrades and they become more vulnerable to further damage. If there are areas beneath the sidewalk and its foundation where air and water can circulate, these spaces can become conducive for tree root growth. Small and fibrous tree roots start off as flexible tissue are incapable of exerting pressure on anything. They mold themselves rather to objects with which they come into contact. During the second and final stage of growth, the same tissues harden in their position and turn into wood. From from this point, the sidewalk can not return to its original position. It is always best to avoid driving on sidewalks with heavy machinery. When building a sidewalk, make sure the foundation is well compacted and deep enough to tolerate environmental conditions. When possible, it is best to avoid building hardscapes at close proximity to trees in order to avoid conflicts.

Myth : Trees have deep roots

Most trees begin life with a taproot – a straight tapering root that grows vertically down and from which other roots sprout. Over time, the roots will reach very deep into the earth and remain mostly vertical.

  • Reality : 

Most trees do not have a taproot; they tend to be more shallow-rooted than you might think. While some trees do have a taproot when they are saplings, after a few years the main root system changes to a widespread system with mainly horizontally growing surface roots and only a few vertical, deep anchoring roots.

Tree roots have to be shallow to stay within the loose, oxygenated soil near the surface. They are extensive, spreading to several times the width of the canopy. Damage to roots is a major cause of decline, death or physical failure. Roots are injured or destroyed by soil compaction, soil removal, severed roots, fill soil over roots, flooding or drought.

Myth : tree wounds must be dressed or coverED

Like animals, trees can be wounded. Dressing the wound by painting over it or stuffing a cavity with material will speed up and complete the healing process.

  • Reality : 

Unlike animals, trees have no wound-healing process. Healing means to restore to a previous healthy state, to repair or replace injured tissues. Trees, with their rigid cell walls, are unable to heal injured or infected tissue. Trees seal off damaged tissue rather than heal it. When tree bark is damaged, microbes attack the plant tissue, and trees respond by creating walls around the tissue. This process is called “compartmentalization,” and it occurs as the tree builds four walls around the injured area in order to preserve the rest of the tree. How well the tree ultimately survives the wound will depend on how successful the tree is at compartmentalizing the damage.

Research shows that wound dressings do not stop decay or stall rot. Trees respond effectively to their wounds without the aid of additional chemicals. Do not interfere with this natural process by applying house paints, wood preservatives or heavy coats of any material to a tree wound. Keep your tree healthy, and it will take care of its wounds. In a short time, the wound surface will blend perfectly with the tree bark.

Myth : prune branches flush with the trunk

Pruning is often done to remove dead wood from a tree, to provide ground clearance, and to promote resiliant structure or to balance weight. To make sure there aren't any ugly stumps left on your tree, clip the branch as close to the trunk as possible.

  • Reality :

The branch collar, which is the part of the branch that meets the trunk, must remain intact for the tree to remain healthy. Cutting a branch flush with the trunk removes the collar, which leaves the tree open to pests, decay and disease. Doing this also interferes with the tree's natural compartimentalization process.


Myth : Topping IS the right choice when pruning a tree

When a tree becomes too tall, it's appropriate to remove all of the highest branches in order to make sure the tree doesn't interfere with the view, sunlight or surrounding structures.

  • Reality :

This practice, known as "topping," is completely unacceptable. It violates all accepted pruning practices. A topped tree is weak and deprived of nutrients from its leaves, which leads to weak branches, pests, decay and disease. Not only that, but it is also expensive to maintain and visually offensive - branches lopped off at arbitrary points and likely to grow back weakly attached and even taller than the original limbs. These vulnerable branches can become susceptible to breaking or falling with little or no cause. Topped trees often need to be removed eventually because they become hazardous over time.

Whenever topping is being considered, there are two acceptable alternatives:

Contact a SIAQ commercial member to learn more about crown reduction (a safe alternative to topping).

Consider removing the tree (if local laws permit) and planting a replacement tree that is appropriate for the conditions of the site.