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Rural Living for January 28, 2010

Pruning Trees

by Carol Dunn

HUERFANO The October weather was rough on Huerfano County trees.  Although most downed limbs have been cleaned up and hauled away, you may still have a job ahead removing unsafe or unsightly broken branches.  It’s safety first and aesthetics next when pruning trees.

    January and February are good times to prune trees.  Trees are less likely to suffer sap loss or invasion of viruses or bacteria after pruning when they are dormant.  Pruned branches also give off an odor that attracts certain disease-carrying insects, and most insects are dormant now also.

    Proper pruning cuts are made where a branch or twig attaches to another.  To avoid stressing the tree, no more than ¼ of the living limbs should be removed at one time.  This ratio is reduced for old trees or stressed trees.  If more pruning is needed, it should be done over a period of years.

    Types of limbs that should be removed include : dead branches; broken branches perched in the crown of the tree; branches that rub or cross another branch; suckers; water sprouts; stubs; and branches arising from narrow V-shaped limb crotches.

    Evergreens generally don’t need pruning unless a branch has been damaged.  They can be pruned any time of year, but pruning when they are dormant will reduce sap flow.

    Wait until just after they flower to prune lilacs and other early-spring flowering shrubs and trees.  Their flower buds form on the new growth they put out in the summer.  Other flowering trees and shrubs, like crabapple, pear, and mountain ash, should be pruned when they are dormant because many are susceptible to fire blight, which can be spread by pruning tools.  If you are pruning off blight damaged branches, sanitize your cutting tool with denatured alcohol or a solution of 1 part bleach to 9 parts water before working on the next tree.  Clean these corrosive materials off tools with soap and water when done for the day.

    The USDA Forest Service recommends several tools for pruning, depending on the job.  Hand pruners work well on limbs up to 1-inch in diameter.  Bypass pruners, good for slightly larger limbs, are also preferable for the smaller limbs because they minimize tearing or crushing of limb tissue.  Lopping shears work well on 2.5-inch diameter limbs, and small pruning saws can be used to cut up to 4-inch diameter limbs.  Chain saws are most effective on removing limbs larger than 4 inches in diameter.  Pole pruners can be used to cut high branches.  Never use pole pruners near power lines.

    “Pruning” 4-inch diameter limbs is not a preferred process, and you should have a good reason to work in a tree with a chainsaw – for instance snow or ice damage.  If you start when your trees are small, pruning them annually as they grow, you should never have to prune anything over an inch or so.

    For detailed instructions on pruning, see the excellent CSU Extension fact sheet on the Internet .