Pruning
Storm Damaged Trees
Nebraska Forest
Service Storm Damage Bulletin No. 3
November 1997
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For the trees that survived the
October snow storm, the job of repairing them and bringing them back
to good health has only just begun. Before broken branches are
removed, they should be examined carefully, and proper pruning
methods should be used to minimize the damage from the pruning cuts.
Trees too large to handle from the ground should be pruned only by
professional arborists. (See bulletin no. 2 for information on how
to hire an arborist.)
Branches to Remove
Safety is the first consideration in
removing branches from storm-damaged trees. All branches that are
loose should be removed as soon as possible to eliminate the chance
of injury or damage if they were to fall. Other branches that are
cracked or broken should be removed after the loose branches are
gone. Branches that did not break under the weight of the snow but
were bent over may have internal cracks or other hidden damage,
especially if these branches have not returned to their original
upright positions. These branches may become hazards in the future
and should be considered for removal. A branch (or trunk) that was
partially stripped of its bark when an attached branch pulled away
should be removed if more than a third of the original circumference
is lost. These branches will always be structurally weak and may
become serious hazards if they are allowed to remain and gain
weight.
Making Pruning Cuts
Pruning cuts should be made so that
only branch wood is removed and the trunk or supporting stem is not
injured. If only branch wood is removed, the wound is smaller, the
tree will be able to seal the wound more effectively, and the chance
of problems with wood decay will be greatly reduced.
To locate the proper place to make a
pruning cut, look for the "branch bark ridge" on the upper
surface of the union of the branch with the supporting stem. This is
a line of bark that has been pushed up as the branch and supporting
stem have grown. Some branch unions will not have this if they did
not form properly. Instead they will have the branch simply pressing
into the supporting stem, forming a sharp V-shaped union. At the
base of the branch, and mostly on the underneath side, look also for
the "branch collar," which is a slightly swollen area of
stem tissue that wraps around the base of the branch. A proper
pruning cut begins just outside the branch bark ridge and angles
down and slightly away from the stem, avoiding injury to the branch
collar. Do not make flush cuts that remove the branch collar. Wounds
created by flush cuts cause substantially more injury to the tree
than wounds left by proper pruning. Branches should be pruned using
a series of three cuts as shown in the figure: two to remove the
weight of the branch (first under then over the branch), then the
final pruning cut.
Branches that have pulled away from
the trunk should be removed at the bottom of the split. Avoid
causing any additional damage to the trunk. Remove any loose bark,
but do not cut into bark that is living and still attached.
When to Prune
The only pruning that really should
be done at this time is the removal of broken branches. Leave the
fine pruning and finishing cuts until late winter or early spring.
All pruning cuts will dry out to some degree during the winter.
Dieback of the inner bark around a pruning cut can be minimized if
the final pruning is left until just before the tree begins to grow
in the spring.
Pruning
"Don'ts"
Never top trees. Topping creates
serious hazards and dramatically shortens the life of a tree.
Never use paint or wound dressing to
cover wounds. These materials do not help the tree and actually
interfere with the tree's wound sealing process.
Additional Information
Learn more about pruning from the
following:
- University of Nebraska publication
Pruning Shade Trees (EC 1224), available at extension offices.
- USDA Forest Service publication How
to Prune Trees, available on the Internet at http://willow.ncfes.umn.edu/ht_prune/prun001.htm.
For more information contact your
local University of Nebraska County Extension Office or visit the
UNL-Nebraska Forest Service Community Forestry web site (http://ianrwww.unl.edu).
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