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  Maintaining Healthy Urban Trees

Single trees on private property and along streets beautify and add value to homes and communities. When trees are removed from an urban environment, because they are dead or dying, gaps are left that may take decades to fill. The trees you own and care for could almost be considered friends or members of the family. They protect against summer heat and function as a windbreak in winter, produce oxygen, and add value to your property. This note aims to advise on how to keep urban trees healthy and to help sick or damaged trees to survive.

Urban stresses. Trees in an urban setting are exposed to stresses unknown to their country cousins. Compacted soil, driveways, streets and underground utility services hamper their root system, causing a shortage of nutrients and water. Shade from large buildings and road salt pollution are detrimental to their survival. To ensure newly planted urban trees' survive, plant them in the right location and in good loose soil. Water and fertilize them regularly. Pruning is essential, particularly when hydro wires and dwellings may interfere with them at a later date. Place mulch and compost around the base of the tree rather than flowers or shrubs. Damage to the roots can severely retard or kill a tree; approximately 90 per cent of a tree's root system resides in the top 30 centimetres of soil. Avoid compacting and suffocation of the root environment. Occasionally, mature trees draw so much water from the soil that the soil shrinks and may cause house foundations to shift, causing considerable damage. If you find these conditions are in evidence, consult the forestry department or your municipality without delay.

Watering. Drought is a greater threat to urban trees than to their forest counterparts. No rainfall for five or six days can seriously affect an urban tree. Though stress may not show immediately, long-term damage will occur; dieback of branches may appear a year later. Therefore, water regularly. In times of drought, grass protects itself by going dormant but trees keep growing; they need your help and protection.

Fertilizing. Don't be too tidy, leave branches, twigs and leaves on the ground, particularly in the fall - they return nutrients to the soil, the lack of which may stress a tree. You may have to consult an arborist who can examine your trees, test the soil and advise you which fertilizer to apply. Avoid fertilizing between August 15 to October 15 as this will interfere with the tree's ability to go dormant. Also, don't fertilize a tree in a year following serious damage caused by storm, ice or other natural disaster. Absorbing fertilizer can be a stress in itself. Apply fertilizer when a tree shows premature loss of leaves or shows signs of wilting.

Pruning. Pruning is an important element in tree management. It maintains health and allows the remaining branches to grow freely. Air circulation within a tree's foliage is extremely important in preventing fungi from growing. Inspect your trees every year for weak, crossed or dead branches. If a branch is broken, remove it as soon as possible.

General Rules of Printing

Prune all dead, weak and diseased branches, making sure to maintain the branch collar.

Don't remove more than one-third of a tree's crown.

If the top is damaged, try to maintain the principal leader to ensure the tree's shape and form.

Only use a chainsaw when trained and experienced and wear protective clothing, gloves, hard hat, safety glasses and steel toed boots when doing more extensive work.

Use proper tools, free of rust and in good working order.

When in doubt engage a professional

Three-cut methods of pruning

A. First undercut the branch at the bottom. Cut half way through the branch moving from the bottom up.

B. The second cut is one-third to one-half the diameter of the limb away from the first cut. Here again, cut half way through the branch. The limb should now fall from its own weight, making sure no damage can be caused by the falling limb.

C. The final cut is next to the trunk. Cut just outside the branch collar with the collar with the lower edge being further away from the trunk. This angle will facilitate the draining of water from the exposed area, preventing moisture from stagnating and causing rot.

Repairing torn bark is essential to the health of a tree. Broken limbs often strip bark causing wounds that invite insect invasion and disease. In order to facilitate healing, use a sharp knife or chisel to smooth the ragged edges, remove all loose bark to the point where it is still firmly attached to the tree. The rounded smooth edges prevent die-back of the inner bark. Do not cover wounds with prepared compounds since they don't help the healing process and often cause decay.

Deciduous trees sometimes lose their tops. The survival of the tree largely depends on how much "crown damage" has occurred. Prune wherever possible to prevent invasion of bark beetles, borers or other insects. A de-stabilized tree can be saved by "cabling and bracing" which is done by an expert. Braces and cables must be adjusted over time to keep in step with the tree's growth. If the top of a young conifer is bent or broken, remove the broken part just above the first set of live branches, bend one of the strongest branches in the first whorl upward and splint it to the rest of the trunk. This limb will take over and become the new leader of the tree. Remove the support when the leader has been firmly established.

Diseases. Trees under stress may be vulnerable to diseases caused by bacteria and fungi. Blotches, leaf spots, blight and discoloration are generally not serious and are part of the forest life-cycle. You may identify a particular disease by the "Field Guide to the Diseases of Ontario". To control diseases a first step may be to keep the area around the tree clean, burn infected leaves and branches (safely!) and fertilize the tree if leaf loss is considerable. Fungicides are available but for extensive work hire a licensed applicator.

Written and condensed by Jan Funnekotter with information derived from the Landowners' Resource Centre and the Ontario Ministry of Natural Resources. For more information about "Maintaining Healthy Urban Trees" and other resource management topics, please contact Jim Hendry, Stewardship Coordinator, P.O. Box 97, Avonmore, Ontario K0C 1C0 or phone 1-(800) 267-1726.



Eastern Ontario AgriNews is published on the third Monday of each month. The printed version is distributed free by postal mail to farms in Eastern Ontario, Canada.

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