5 P.M. INTERVIEW: Pruning trees

CHIPPEWA COUNTY, Wis. (WEAU) -- Why prune trees?
Pruning is important for a variety of reasons. Pruning can help control the size of a tree, direct growth, influence flowering or fruiting, or maintain plant health and appearance. Pruning can also increase the safety of a tree by removing broken, diseased, dead, or dying branches.

What should be pruned?
Newly planted trees: Newly planted trees should not be pruned unless a branch is broken, diseased or dead. These trees need foliage to produce carbohydrates (sugars) that are then transported to the root system for initiation of new roots.
Young trees: After a young tree is established for two to five years, the tree can be pruned to encourage a well-branched canopy. Lower branches can be removed to raise the canopy, if desired. Scaffold branches to be maintained in the tree should be selected such that they are 12-18 inches apart, are evenly distributed around the trunk and have wide crotch angles. Remove no more than 1∕3 of the total crown of a tree at one time. Young trees also need corrective pruning to remove crossing branches, double leaders, watersprouts, and root suckers.
Older trees: Older, established trees, if properly trained when young, require little pruning. These trees should never be topped as this leads to poor branch structure and increased limb breakage. Use the three-point method of limb removal for pruning large branches.
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When should I prune trees?
Most deciduous trees should be pruned in late fall to winter. At this time of year, you can see the overall branch structure easily, and most insects and disease causing organisms are not active. Late fall/winter pruning is especially important for oak trees to help prevent spread of the fungus that causes oak wilt. Late spring and summer are usually not good times of year to prune because disease pathogens are present and wound closure is slower. If you prune in late winter, some trees may bleed or ooze sap excessively in the early spring. The bleeding may be unsightly, but does not harm the tree. Examples of trees that bleed excessively are maple, willow, birch, walnut, beech, hornbeam, elm, and yellowwood.