Extension Communications
3614 Administrative Services Building
Ames, Iowa 50011-3614
(515) 294-9915
1/7/02
Contacts:
Sara Helland, Plant Pathology, (515) 295-0589,
sarathom@iastate.edu
Jean McGuire, Continuing Education and Communication Services, (515) 294-7033,
jmcguire@iastate.edu
Yard and Garden Column for the Week Beginning January 11, 2002
Time to Prune Deciduous Trees
By Sara Helland
Research Associate
Plant Pathology
Iowa State University
Many people think that the winter is a season to relax in front of the fire and take a break from the garden. However, our deciduous ornamental and fruit trees need us to bundle up and head outside. Winter is the best time for pruning. Trees are dormant and many pathogens are absent so a wound in the tree is less likely to result in infection. Deciduous ornamental trees flowering after May should be pruned between January and March. These include trees like oaks, elms and maples. Deciduous fruit trees should be pruned in late winter.
There are a number of reasons for pruning trees. It is important to remove dead and diseased tissue before the infection spreads to the rest of the tree or to neighboring trees. If your fruit trees are getting too large, pruning is a good way to keep them "dwarf" size. Prune young trees to develop a healthy branching structure that is important to a long life as beautiful mature tree.
Establishing a scaffold (the main branches of a tree that determine its shape) while a fruit tree is young results in good fruit crops and reduced disease in later years. If the canopy is too thick, pruning will open it up. It will increase air flow and sunlight thus reducing disease and insect infestation. Trees also can be pruned for your safety. Remember those annoying low-hanging branches in your yard last summer? Pruning these branches now is a healthier option than breaking them off with your head while mowing next summer.
Before beginning your winter pruning get the necessary tools. Use hand pruners to trim branches up to 3/4 inches in diameter. Bypass blade pruners, with a curved head, are the best option for these thin branches. Use lopping shears, with long handles and a bypass blade, for branches 1-3/4 inches in diameter. Use fine- or coarse-toothed pruning saws to trim branches three inches in diameter, as well to remove smaller branches in tight areas where hand pruners or loppers can't reach. Use chain saws for larger jobs.
Trim branches at the intersection of two limbs or between the branch and the trunk. Make the cut at the outside edge of the swollen, rough area at this junction, called the bark ridge. Hold shears the at a 40 to 65 degree angle from the bark ridge. Don't trim too far away from the bark ridge or you'll leave a big stub of branch sticking out. This provides bacteria and fungi an entrance point when spring arrives.
Never "top" your tree by trimming upper branches through their middle. This results in more growth and possible infection sites, and you may find yourself standing in the cold even longer next winter. Prune away "suckers," the branches that persistently grow up from the base of the tree, by cutting them at their base.
The rules for pruning are not hard and fast and your best bet is to cut in places that seem like natural branch points in the tree. Please contact your ISU Extension county office for more information on pruning methods.
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