Container grown plants normally require little pruning at planting time, other than the removal of parts damaged by handling in transit, since there has been no reduction of the root system.

As the shade tree grows, routine pruning should be carried out to ensure the natural symmetrical shape of the tree. As a rule the interior of trees are kept open to allow good air circulation. Dead, diseased, broken, and interfering branches are removed.

Note: When pruning, all cuts must be made clean and close to the stem. Jagged cuts do not heal readily and create sites for disease development. Clean the tools with rubbing alcohol before you start pruning, and clean again after each tree to prevent the spread of disease.

When pruning a tree you should keep in mind that in order for the tree to survive it must be able to defend the open wound. The more you do to help the tree heal itself, the more likely it is to survive. You can promote rapid and complete healing by not cutting through the tree’s natural protective barriers. Looking carefully at the tree you will see a bulge at the point where the branch joins the trunk. This bulge is known as the branch collar. Inside the branch collar are terpines (in conifers) and phenols (in hardwoods). These are the chemicals that protect the tree from invading pests and diseases. Cutting a branch off flush with the trunk destroys the branch collar and gives the tree little defense against marauding insects and fungal infections.

Use the following procedure for pruning a branch. Always use a good pruning saw for branches thicker than 1.5". Japanese saws are excellent, giving a smooth cut with little tearing of bark. You may use bypass hand pruners or bypass loppers for smaller branches. Bypass blades make a cleaner cut than the anvil type which tends to crush the stem as it cuts. Using hand pruners, cut as close to the branch collar as possible but not into it. Hold the pruners with the blade side toward the tree (for the smoothest cut) and grip the branch with your other hand. Gently push down on the branch as you squeeze the pruner. This makes cutting much easier. If you have trouble finding the branch collar-they are nearly flat on some conifers - first locate the branch bark ridge, the raised bark between the bark and trunk, and then make a cut at an angle that mirrors the angle between the branch bark ridge and the trunk .

For branches larger than 1.5" diameter, first stub cut the branch six inches out from the branch collar. Use a pruning saw and make the first cut up from the bottom halfway through the limb. Make the next cut down from the top and right through the limb. This procedure prevents the weight of the limb from pulling down and tearing out a long strip of bark and wood towards the trunk. Now that most of the weight of the branch has been removed, you can safely make the final cut. Make your saw cut as close to the branch collar as possible but don’t damage it.

As a general rule, the best time to prune broadleaf trees is late dormant season (late March to mid-April in our area), but some trees (maple, birch, mulberry) may "bleed" and are best left until later in the year . The best time to prune evergreens is early summer (late June). For ornamental purposes, you may wish to delay pruning flowering trees until after they bloom. This is acceptable, however don’t prune when the food reserves are low. Food reserves are lowest just after leaf formation, so you can wait until mid-June, especially if cuts over 1 1/2’ (cm) in diameter must be made. At this time the cambium tissue is active and healing can immediately take place.

In the years following branch removal you will see the branch collar growing over the wound. It should grow evenly all around the cut. If the cut was made too close to the trunk (i.e., damaging the branch collar) the wound-wood will be seen growing over only the sides of the wound.

When cutting back the ends of branches always cut close to a bud or secondary branch. Make sure the bud or secondary branch is pointing in the direction that you wish the tree branch to grow

There are three common types of tree injuries: damage caused by weather (where limbs are torn off by gusts of wind, lightning strikes or the weight of ice and snow), damage caused by automobiles or machinery (usually limited to bark or sapwood being ripped from the tree) and damage caused by animals, the most serious of which is girdling (where the bark is chewed off the trunk in a band completely around the tree). If girdling isn’t repaired the tree will die.

After a storm assess the damage to your tree. If it has been hit by lightning, determine how much of the bark has been affected. A lightning strike often transmits enough energy to the tree to boil the liquids inside. The boiling creates steam, forcing the wood to split open and the bark to peel away.

If a strip of bark has come off all around the circumference of the tree, unless you attach a bridge graft the life support to the roots will be severed and the tree will starve to death within a year. If six feet (1.8m) or more of bark has split away all around the trunk, the tree can also be saved by bridge grafting: however, the resulting repair will be so disfiguring that it’s usually better to cut the tree down.

Torn Branches

Wind, ice or lightning can also rip off branches (as can undue contact with cars or machinery). If a fractured stub remains it should be cut back to the branch collar (the bulge where the branch joins the trunk). Don’t cut the collar off as it protects the tree from insects and fungal infections.

If the branch was torn off at the trunk, a more serious wound has occurred. The exposed sapwood should be smoothed (with a chisel, gouge or sharp adze) and the frayed bark trimmed back to where it is still firmly attached to the tree. As you trim back the bark, smooth the opening into a shape that resembles an upside-down flame; the downward flow of food will move more easily around this shape than any other.

TREE PAINTS

The controversy surrounding tree paints, which are used for sealing wounds, is never-ending. Paint or tar-based wound dressings are of little use and sometimes even harm the tree by trapping microorganisms under the skin, providing a cozy breeding ground. The best wound dressing comes from inside the tree itself. However, recent research has shown dressings that form a plastic-like sheet speeds callus formation. If the wound is large, painting may be more valuable for aesthetic reasons. Stay away from compounds that form thick skins and tend to peel away from the wood surface, providing a nesting site for insects and micro-organisms.

 Girdling

A girdled trunk is one of the gardener’s worst nightmares. It’s usually caused by hungry mice, rabbits or deer looking for food while the ground is covered with snow. It can also be caused by the careless use of a string trimmer. This wound is serious not just because it will kill the tree if left alone, but because most gardeners don’t know how to treat it.

The procedure to repair a girdling wound, called bridge grafting, is quite simple and if done carefully is usually successful. By using a simple graft to join the two disconnected sections of bark, a new path is provided for foods traveling from the leaves to the roots.

A small tree of one inch (2.5 cm) in diameter can be saved by one bridge. Larger trees should have a bridge for every inch (2.5 cm) of trunk diameter. In grafting terminology the bridges (thin, flexible branches) are called scions. Grafting must be carried out as soon as the scions are cut.

Bridge Grafting Procedure

1. Trim back through sections of bark.

2. Using a sharp knife, collect the scions from the branches of the affected tree or from another tree of exactly the same genus and species. Take last year’s growth, either dormant or freshly foliated.

3. The scions should be collected in such a way that you will remember which is the apical end (the end pointing toward the branch tip) and which is the basal end (the end pointing towards the main trunk). this can be accomplished by making a square cut on the basal end and a sloping cut on the apical end. This is important since the scion must be inserted with the apical end pointing up. Always make the end cuts on the scion wood near a bud, as it’s here that most growth activity occurs.

4. One of the most successful graft types is the inverted L rind bridge graft. This must be done in late spring and early summer, when the bark lifts away from the cambium easily.

5. Make an inverted L cut into the bark a short distance below and above the girdle. The cut should be just wide enough to hold the scion. Make sure it passes through to the sapwood (if the bark won’t lift off you haven’t cut far enough).

6. Twist the knife and the bark should lift away from the sapwood right at the cambium layer (a thin layer of green tissue).

7. Turn the square cut on the basal end into a sloping cut to match the one on the apical end.

8. Insert the ends of the scion under the bark , taking note of which end is pointing up and making sure there is good firm contact between the scion and trunk’s cambium.

9. Tack the scion in place with a small nail. Make sure it’s bowed in the middle away from the trunk to exert pressure under the bark at both ends. Seal the grafts with grafting was.

(Some information on this page courtesy of Lee Valley Tools: used with permission)