Extension News

Winter Pruning of Deciduous Trees and Other Activities

Note to media editors: This is the Garden Column for use during the week beginning Feb. 6.

2/2/2009

By James Romer
Extension Horticulturist
Iowa State University

This time of the year gives many gardeners an empty feeling. It is hard to keep warm and dry when temperatures dip below zero and it snows every other day. It is reminiscent of those classic song lyrics -- "All the leaves are brown and the sky is gray ... California dreamin' ...." Anyway, this is a great time of the year to do some planning and pruning.

The late dormant period (February to early April) is an excellent time to prune deciduous trees. The absence of foliage at this time of year gives the home gardener a clear view of the tree and allows him/her to select and remove appropriate branches. Proper pruning improves the appearance, maintains the health and prolongs the life of trees. Improper pruning destroys their natural beauty, weakens them and may lead to their premature death.

It is essential to make proper cuts when pruning trees. Do not make flush cuts. Flush cuts are cuts made as close as possible to the trunk or main branch. Flush cuts produce large wounds, destroy the tree's natural mechanisms that promote healing and slow the “healing” process. When pruning trees, make the final cut just beyond the branch collar and branch bark ridge. The branch collar is the swollen area at the base of the branch. The branch bark ridge is the dark, rough bark ridge that separates the branch from the main branch or trunk. Pruning just beyond the branch collar and branch bark ridge retains the tree's natural defense mechanisms and promotes the healing process. When a branch is pruned properly, a slightly raised area remains on the trunk or main branch. However, do not leave stubs.

Do not apply wound dressings to pruning cuts. The application of wound dressings or paints doesn't stop decay and may actually inhibit or delay the healing of wounds. There is one exception with not applying paint to oak trees. Oak wilt is a fungal disease that is lethal to many oaks. Oak wilt infections occur most commonly in spring and early summer and are spread from infected trees to healthy trees by sap-feeding beetles. To reduce the risk of the spread of oak wilt, don't prune oaks from April 1 to July 1. If oak trees must be pruned between April 1 and July 1, for example, to correct storm damage, immediately apply a latex paint to all cut surfaces to avoid attracting sap-feeding beetles to the wounds.

Use the three-cut procedure when cutting large branches to prevent extensive bark damage. Make the first cut about one to two feet from the main branch or trunk. Cut upward and go about halfway through the branch. Make the second cut a few inches beyond the first. Cut downward completely through the branch. Make the final cut just beyond the branch collar.

Some trees, such as maple, birch and elm, bleed heavily when pruned in late winter or early spring. However, the heavy bleeding doesn't harm the trees. (The trees won't bleed to death.) Eventually the flow of sap will slow and stop. Heavy bleeding of susceptible trees can be avoided by pruning in late June or early July.

The pruning of deciduous trees by the home gardener should be limited to small trees and the removal of smaller branches that can be reached from the ground in medium to large trees. Branches high up in large trees and those near utility lines should be left to professional arborists. Professional arborists should have the proper training and equipment to safely perform the job.

If that’s not enough to do, another enjoyable winter activity is to leaf through garden catalogs. Many contain colorful plant photographs. Some carry specific merchandise, such as seeds, perennials, roses or fruits. Others carry a wide variety of products.

Also, visit a bookstore or public library and browse through some of their gardening books. Excellent reference books for home gardeners include "Manual of Woody Landscape Plants" by Michael Dirr; "Continuous Bloom" by Pam Duthie; "Herbaceous Perennial Plants" by Allan Armitage, and many others. Remember also that your Iowa State University Extension county office has numerous publications on gardening in Iowa. Most of these publications also are available from the ISU Extension Online Store at www.extension.iastate.edu/store.

So get busy planning, pruning and dreaming about plants for this spring.

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Contacts :

James Romer, Horticulture, (515) 294-2336, jromer@iastate.edu

 

Del Marks, Extension Communications and External Relations, (515) 294-9807, delmarks@iastate.edu