Tuesday, March 27, 2012

Backyard Woods - Pruning tools and techniques

Which pruning tool should I use?
The choice of tool depends largely on the size of branches to be pruned and the amount of pruning to be done. Use hand pruners on small branches (under 1 inch diameter). Cut larger branches (up to 2 inches) with lopping shears. Hand pruners and lopping shears are available in anvil and by-pass cutting styles. The anvil style cuts the branch between a straight blade and an anvil or block. The by-pass style uses a curved cutting blade that slides past a broader blade, much like a scissors. To prevent tearing or crushing of branches, the by-pass style cutting blade is the best.
Use a pruning saw for branches 2 to 4 inches in diameter. Unlike most other saws, pruning saws are designed to cut on the "pull-stroke."
A chain saw is preferred when pruning branches larger than 4 inches. Safety dictates not using a chain saw above shoulder height and using additional safety equipment. To avoid the need to use a chain saw, prune when branches are small. Also, a small branch leaves a small wound and generally heals faster.
To cut branches beyond reach use a pole pruner. Generally, pole pruners have a pruning head (similar to a lopping sheer) and a pruning saw. The pruning head can cut branches up to 1.5 inches; and once again, the by-pass style is preferred.
Sanitizing tools helps prevent the spread of disease from infected to healthy trees. Tools become contaminated when they come into contact with fungi, bacteria, viruses, and other microorganisms that cause disease in trees. Pathogens need some way of entering the tree to cause disease, and fresh wounds are perfect places for infections to begin.
Sanitize your tools by using either 70 percent denatured alcohol or a solution of 1 part liquid household bleach to 9 parts water. Before making each cut, immerse the tool in the solution for 1 to 2 minutes, and wipe wood particles from the cutting surface. Bleach is corrosive to metal surfaces, so when you are finished pruning clean tools thoroughly with soap and water.
Tool sanitation is not needed during the dormant season.

Where and how do I make pruning cuts?
Make pruning cuts at a node, the point at which one branch or twig attaches to another. In spring growth begins at buds, and twigs grow until a new node is formed. Remove only branch tissue and take care not to damage stem tissue so it will not decay, and so the wound will heal more effectively.
To find the proper place to cut a branch, look for the branch collar that grows from the stem tissue at the outside of the branch. On the upper branch surface, there is usually a bark ridge that runs (more or less) parallel to the branch angle, along the stem of the tree. A proper pruning cut leaves both the branch bark ridge and the branch collar intact.
You can evaluate the quality of pruning cuts after one growing season. A concentric ring of woundwood forms from proper pruning cuts. Improper cuts made inside the branch bark ridge or branch collar result in pronounced development of woundwood on the sides of the pruning wounds and very little woundwood on the top or bottom. A cut too far from the stem leaves a branch stub, and wound closure is delayed because the woundwood must grow over the stub.

Branches large enough to require saws should be supported with one hand while the cuts are made. If the branch is too large to support, make a three-step pruning cut to prevent bark ripping.
1. The first cut is a shallow notch on the underside of the branch, outside the branch collar. This cut prevents the falling branch from tearing the stem tissue.
2. Make the second cut outside the first cut, all the way through the branch, leaving a short stub.
3. Cut the stub just outside the branch bark ridge and branch collar, completing the operation.

Prune dead branches the same way you would live branches. Making the correct cut is usually easy because the branch collar and the branch bark ridge continue to grow and can be distinguished from the dead branch. Make the pruning cut just outside the ring of woundwood tissue that has formed, being careful not to cause unnecessary injury. Large dead branches should be supported with one hand or cut with the three-step method.

Can I harm trees by pruning?
Topping and tipping are pruning practices you should not use. Topping is the pruning of large upright branches to reduce the height of a tree. Tipping is the cutting of lateral branches to reduce crown width. Both practices result in the death of the cut branch back to the next lateral branch below and the development of numerous sprouts. These sprouts are weakly attached to the stem and eventually will be supported by a decaying branch.
Improper pruning cuts cause unnecessary injury and bark ripping. Flush cuts injure stem tissues and can result in decay. Stub cuts delay wound closure and can provide entry to canker fungi, delaying or preventing woundwood formation.
Avoid producing "lion’s tails" (tufts of branches and foliage at the ends of branches) caused by removing all inner lateral branches and foliage. Lion’s tails can result in sunscalding (bark damage caused by freezing and thawing), abundant branch sprouting, and weak branch structure and breakage.

Should I treat tree wounds?
With the exceptions noted below, do not apply wound dressing. Tree sap, gums, and resins are the natural means by which trees combat invasion by diseases. Although unsightly, sap flow from pruning wounds generally is not harmful. Wound dressings will not stop decay or cure infectious diseases. They may actually interfere with the protective benefits of tree gums and resins, and trap moisture behind the dressing and promote the growth of wood-decaying fungi.
The only benefit of wound dressing, such as you can buy at farm and garden stores, is to prevent introduction of oak wilt and Dutch elm disease. When oaks and elms are wounded accidentally or by necessary pruning during the critical time of the year (usually spring for oaks, and the entire growing season for elms), apply some type of dressing to the wound immediately after it is created.

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