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Winter Pruning Helps Keep Trees Healthy, Happy

photo by Knilram
Flickr/Creative Commons

Winter is a key time for pruning trees to keep them healthy. KUNC gardener Tom Throgmorton says it’s especially important if trees have been damaged by Mother Nature.

With the leaves off of the trees, damage from the fall snow storms is even more evident.  Most certified arborists agree -- winter is the season to prune trees to strengthen the tree and clean up the damage. 

Leafless trees allow arborists easier, faster access.  It makes their job more efficient.  They can see what they’re doing.  But even without leaves some of the storm damage can’t be seen from the ground. 

Trees store energy in other tissues once they lose their leaves.  Any injury, like a pruning cut, becomes a priority for the stored energy.  The plant uses the stored reserves to compartmentalize and close off that injury.  During the winter most of the plant’s fuel can be directed at healing the pruning cut. 

Winter pruning gives more time for wounds to close and harden-off.  This is important so wood boring insects can’t easily damage a tree.  American elms are usually pruned during the winter months.  The insect that transmits Dutch Elm disease can’t enter through a hardened wound. 

Apple, mountain ash and pears should also only be pruned when they’re dormant.  They are all susceptible to fire-blight.  Fire-blight enters trees through open wounds.  Winter pruning lets the wound close and reduces the risk of fire-blight infection. 

Maple, birch and walnut trees bleed sap when they’re pruned.  Cuts on large old trees look really messy.  Some studies show the heavy sap run may help the tree heal faster.  The studies indicate the sap is a natural wood preservative.  So even though it looks bad the sap flow is beneficial.

The only time winter pruning may not be a good idea is when a tree has a lot of dead branches in it.  The tree needs all of the live, sound branches it can keep for its own health.  Pruning during the growing season assures all of the dead branches get cut out. 

Many trees are neglected.  They only get pruned by high wind storms or heavy snows.  Studies show well maintained trees withstand this storm pruning.  These trees are healthier and live longer.  Contact a local, certified arborist to prune and maintain your tree investment.



Tom has been offering garden advice on KUNC for almost two decades. During that time he has been the wholesale sales manager at Ft. Collins Nursery, Inc. Since January of 2005 he has been the owner and operator of Throgmorton Plant Management, LLC., a landscape installation and maintenance company as well as a horticultural consulting firm. He lives in northern Ft. Collins with his wife and two kids.
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