Landscape - Dormant Season Pruning Guidelines

The winter season is fast approaching. Landscape maintenance companies will schedule dormant pruning during this period. The following is an article on dormant season pruning. Although geared toward trees, the concepts equally apply to shrubs.

Under optimal growing conditions, the appropriate time to prune will depend on the type of plant, its condition and the desired results. During the winter months, a closer inspection of the interior growth habit, or skeleton, of the tree or shrub can often reveal several maintenance issues that might have otherwise gone undetected due to the cover of foliage. Dormant landscape pruning can be a very effective and cost efficient method in controlling the future growth and overall health of your landscape investment.

The need for proper pruning and decision-making cannot be overemphasized. Visualizing the end product of your actions can be extremely difficult. Periodically stepping back to inspect the form and structure while pruning can be an invaluable method in avoiding the chance of over-pruning. Under normal circumstances, no more than twenty-five percent of the current crown should be removed during a given year.

Pruning is by definition the controlled wounding of the plant for a specific purpose or desired effect. The specific type of pruning necessary to maintain a tree in a healthy, safe and attractive condition has recently been defined in a national set of standards. These classifications can easily be applied to shrubs and other ornamentals throughout the landscape.

>Crown Cleaning: The removal of dead, dying, diseased, crowded, weakly attached and low-vigor branches from the crown of the tree.

>Crown Thinning: The selective removal of branches to increase light penetration and air movement through the crown. Thinning opens the foliage of a tree, reduces weight on heavy limbs, and helps retain the tree’s natural shape.

>Crown Raising: Removes the lower branches from a tree in order to provide clearance for buildings, vehicles, pedestrians, and vistas.

>Crown Reduction: Reduces the size of a tree, often for clearance for utility lines. Reducing the height or spread of a tree is best accomplished by pruning back the leaders and branch terminals to lateral branches that are large enough to assume terminal roles. This method replaces the unethical practice of topping, which is the indiscriminate reduction of a tree’s canopy.

Most routine pruning to remove a flush of growth, weak, diseased or dead limbs can be accomplished at any time of the year. However, there are several major benefits to timing routine or maintenance pruning during the winter months. Trees produce a dense crown of leaves to manufacture the sugar used as energy for growth and development. Pruning trees and shrubs during the dormant season does not interrupt this nutrient and growth cycle, and can result in an efficient re-direction of growth during the following spring. Dormant pruning reduces the number of buds or growing tips sharing the stored food reserves from the roots, so each remaining bud can grow more vigorously the following spring. Dormant pruning of summer flowering shrubs, whose flower buds are formed on new growth, will also encourage larger flowers.

Some trees, such as maples and birches, tend to “bleed” if pruned during the late winter or early spring. Though by itself of little consequence to the health of the tree, these unsightly stains and wounds may create an issue with some of your clients. Information provided prior to any late winter season pruning should address this issue.

Disease and pest management are also crucial in scheduling winter pruning. Oaks and elms are prime examples of where winter or dormant pruning may be preferred. Oak wilt diseases are active during the growing season, and fresh pruning wounds can allow spores access into the tree. Untreated saws can also inadvertently spread the disease from cut to cut. Wood borers that may be carrying Dutch Elm Disease spores will also utilize fresh spring pruning cuts as an entrance to previously unaffected trees. Winter pruning of evergreens will least likely attract borers. Timed properly, pruning may actually reduce the need for additional chemical pest control and disease suppression throughout the growing season. Knowing the biology of these and other pests and how they may interact with your pruning decisions and expertise will be the key to creating and maintaining a successful, healthy and aesthetically pleasing landscape for years to come.

Article reprinted from "Dormant Season Landscape Maintenance: The Benefits of Winter Pruning" by Nicholas Polanin, Agricultural Agent, Rutgers Cooperative Extension of Somerset County, in the March 15, 2007 edition of the Landscape, Nursery, and Turf edition of the Plant and Pest Advisory from Rutgers (NJ) Cooperative Extension.