Urban Forest Plan

Severely Storm Damaged Pine, Kingston Field
11. Severely Storm Damaged Pine,
Kingston Field

Spruce Planted Too Close to Harrison-LeCaine Hall
12. Spruce Planted Too Close to
Harrison-LeCaine Hall

4    The Need for Money, Staff and Life Cycle Approach

The campus landscape shows signs of neglect and overuse. Shrinking grounds maintenance budgets have not provided the resources required for a comprehensive program of continual maintenance. The University’s current grounds staff of six persons is inadequate for such a program on two campuses with approximately 1,800 trees and some 22 hectares of landscaped areas. Over the years, grounds improvements have also not kept pace with that of new buildings. Many areas of the campus have not been properly designed or systematically upgraded to accommodate the changing needs of pedestrians and vehicles, or to provide a suitable growing environment for trees. Grounds improvements are therefore needed and long overdue.


The ice storm of 1998 has pointed out the vulnerability of trees to nature’s devastating impact. Many of the mature trees suffered severe crown loss from the weight of the ice. The damage could have been lessened if these trees had a history of regular pruning. Pruning aids in the establishment of a strong structure, allowing light and air to penetrate the crown which in turn reduces the possibility of insect and disease. The thinning out of the crown and the removal of unsafe dead and diseased limbs reduce the number of limbs where ice can collect, thereby reducing the weight of ice on the crown. Pruning also reduces the sail of the tree allowing the wind to penetrate the crown.

Pruning should be initiated after a tree becomes established (2 - 3 years after planting) because this aids young trees to develop into structurally strong trees, well suited to their site and their function. When pruning is done early, less corrective pruning is needed as trees mature.

Corrective pruning must be undertaken to storm damaged trees that are deemed viable. The purpose is to remove damaged and unsafe limbs and install cables to help support limbs and crown structure. However, it is imperative that as much of the crown be left intact as feasible because the tree requires its leafy area for photosynthesis.

All pruning should be carried out in accordance with ANSI A300-1995 Standard Practices for Tree, Shrub and Other Woody Plant Maintenance.

Cabling and Bracing

Cabling is the installation of flexible steel cables between tree limbs to limit excessive movements or to reduce stress on a weak branch union. Cables provide support or limit movement in leaders with "V" branch unions with included bark. They are also installed to support long, heavy horizontal branches and decayed limbs.

Bracing is the installation of wood screw rods or machine threaded rods to strengthen weak crotches, repair splits and hold rubbing limbs together or apart.

Cabling and bracing are techniques that stabilize weak branch unions and limbs to reduce the risk of limb and crown failure. They are used when pruning cannot correct deficiencies and structural weaknesses. This occurs most commonly in trees that were not pruned properly or routinely when young. Therefore, reducing structural defects by proper pruning reduces the need for structural supports later in the life of the tree.

As a tree matures, cabling and bracing become more important for maintaining crown stability. Structural defects develop from decay associated with wounding, storm damage, and pests. Mature trees do not benefit from radical pruning; subsequently cabling and bracing are important considerations for their management.

A large percentage of the Norway Maples throughout the campus have weak branch unions and require cabling; a number of the Lindens, Silver Maple and various other trees also require the same attention.

All cabling and bracing should be carried out in accordance with ANSI A300 specifications.


Soil and nutrient management are key aspects of a total Plant Health Care Program. The soil provides the root system with water, oxygen and nutrients that are required for photosynthesis and respiration.

In a natural forest setting, nutrients are returned to the soil when leaves, needles and wood are left to decompose. These materials break down into humus and fine organic soil components that the plant utilizes. However, in an urban setting leaves, grass and other organic matter are removed off the site. Breaking this cycle of decomposition depletes the soil of key elements over a period of time; the remaining nutrients are inadequate to supply the needs of a tree. Trees that are nutrient deficient grow more slowly and are susceptible to injury from drought, air pollution, soil compaction, extreme temperatures and insect and disease. All these factors have an impact on the appearance and shorten the lifespan of trees and shrubs.

Trees and shrubs require 16 essential elements to grow; three of these--Carbon, Hydrogen and Oxygen--are absorbed from air and water. The remaining elements are absorbed from the soil via the root system. These are: Nitrogen, Phosphorus, Potassium, Calcium, Magnesium, Sulfur, Boron, Copper, Iron, Manganese, Molybdenum, Zinc and Chlorine.

Fertilizer can be applied in three ways: granular surface application, liquid injected into the ground, and liquid injected into the trunk. It is generally preferable to inject the liquid into the ground (root fertilization) as this method benefits the tree in two ways: adding nutrients to the soil and aerating to lessen compaction. The use of Nitrogen in a slow release, specially formulated, organic base along with other micro-nutrients (30-8-8) is recommended. This formula will enable the tree to uptake the fertilizer for as long as two years.

It would be prudent to begin fertilizing the trees which have been affected by the storm damage (and have been deemed viable) and those with insect and disease problems. A long term program needs to be established so all trees are fertilized every 2 - 4 years. The exception would be trees in a mulched bed encompassing the total root system.

All fertilizing should be done in accordance with ANSI A-300 specifications.


Mulching involves the placement of a layer of organic material on the soil surface over the tree’s root zone. It provides the following benefits:

  • Reduces evaporation from soil surface thereby reducing the need for watering.
  • Moderates soil temperatures.
  • Reduces soil compaction by dispersing the load over a greater area.
  • Reduces potential for soil erosion by eliminating direct soil-water and soil-wind contact.
  • Allows a layer of organic material to build up that can supply the root system with nutrients.
  • Helps to eliminate weed and grass growth around trees, lessening the competition for nutrients.
  • Reduces the need for mechanical equipment (lawnmowers and weedeaters) to be near the trunk of the tree, thus lowering the potential for trunk injury.
Suitable mulch materials include: wood chips, bark, leaves, needles and compost. The use of inorganic materials such as rocks, landscape materials, plastic, etc. should be avoided, as they breakdown slowly or not at all.

The following guidelines should be observed when applying mulch:

  • Apply mulch from dripline to root collar. Do not place the mulch against the tree trunk as this may result in disease.
  • In a lawn setting, it is best to cut the grass very short and then apply the mulch directly on top. A plastic barrier is not needed.
  • The mulch layer should be 2 to 4 inches deep. Additional mulch should be added whenever necessary to maintain this depth.
Mulching would be an effective way to provide a natural environment under groves of trees, e.g., in Summerhill Park where the grass under the trees cannot be sustained due to lack of sunlight, around newly planted trees, and to create natural pathways (to lessen soil compaction). It will reduce the amount of fertilizing and watering.

Insect and Disease Management

Insects and diseases may become serious threats to a tree’s health. Environmental stress weakens plants and makes them more susceptible to insect and disease attack. Disease organisms and insects commonly attack an already stressed tree, adding further damage to the existing symptoms. Therefore, by providing a healthy environment, the tree increases its natural defenses.

While preventive maintenance is preferred, there are times when chemical interventions are necessary. Trees known to have an insect/disease problem should be monitored on a regular basis for health status and the presence of any insects and disease so problems can be found and solutions undertaken quickly. When possible, insects should be controlled using cultural and manual methods. If pesticides are the only solution, non-toxic products such as soap or horticultural oil should be used. Synthetic pesticides and insecticides should be used only as a last resort. The treatment method used for a particular insect problem will depend on the species involved and the extent of the problem.

Blanket cover sprays are no longer utilized as it is well known that many insects are beneficial rather than destructive; they help act with pollination or act as predators of more harmful species. The timing of the treatment is crucial; it will only be beneficial if applied at the appropriate life cycle of the insect.

Some species of trees noted on campus are already infected with insects and disease: the Austrian Pine with Diplodia tip blight, Blue and White Spruce with Cytosphore Canker, Norway Spruce with Spruce gall aphids, Birch with Bronze Birch bore. These trees require the application of appropriate controls to eliminate the spread of the insects and prevent the possible loss of the tree. In addition, it would be prudent to deep root fertilize the affected trees as insects and disease only attack a tree in a weakened state of health. Maintaining good health will lessen the possibility of a tree requiring costly treatments.