Winter, What's it Good For?

Stop for a moment and think, winter. That’s right, the joys of winter. With summer behind us and the Lawn Boy put to bed, it’s time to dream about those winter activities we hold so dear. Fall brought mulch and fertilizer to our precious garden soil, while leaves have been collected and composted for next year’s mulch. Soon, Thanksgiving and Christmas will be in full swing and Sunday’s will be reserved for singing with the Fat Lady. Skiing at our favorite downhill or cross country haunts, sledding, snow forts, caroling, and hot cider are the gifts of winter. All contribute to family, friends and traditions that have helped shape this country into what it is today. These activities, however, are but harbingers of winter, only miniscule pieces of our Mid-Atlantic dormancy. The above pleasures are merely life at its mediocre best. Only those who have discovered life’s richest offerings, realize that winter is the time to prune many of our precious trees and shrubs. It is for this reason our earth’s blessed warmth bows to winter.

I’m sure there are those who have not yet found this joy and are right now asking themselves, “why do we prune plants in the winter and… which woody plants are suitable candidates? Let’s see if we can clarify, and have fun while we try. Pruning, when understood, is fun and brings special blessings only spring can provide. Don’t get me wrong, I’ve killed a few shrubs during my career, but as a rule most look darn good after some well thought-out effort.

Within our landscape design, many plants are grown for their foliage and others for flowers. Can you give examples of plants used for foliage? This group contains things such as boxwood, holly, heavenly bamboo or nandina, and barberry to name a few. Remember, all these woody plants have flowers that are insignificant which are not as important to us as they are to the plant. Wouldn’t it be simple if we could use the rule, “if the flower is insignificant, prune it in winter”? I’m afraid it’s not quite that simple. There are always plants that insist on dancing to their own music, that can’t be part of the norm, (if there is a norm in nature). Nature, in all her splendor, insures diversity which contributes to what one of my mentors calls, “order within disorder”. Nature is also flexible, but only to a point.

On the other hand can you think of a plant with significant flowers that we prune in winter? How about glossy abelia, rose of Sharon, certain hydrangea or our ever-popular crepe myrtle? All of these beautiful flowering plants take a dormant season pruning because they flower on wood produced during the current growing season. In contrast, plants such as mountain laurel, rhododendron, azalea, forsythia, some spirea, deutzia, flowering quince, pieris and others are pruned after flowering because they flower on wood produced during the previous year’s growing season. Pruning these plants in winter denies us the very essence of their existence. Imagine a spring without roadways bill boarded in a pastel mural of redbud, (e-mail me and I will relinquish my secret locations), without front yards splashed in a rainbow of azalea, forests sprinkled with a snowfall of serviceberry or yards covered in white blankets of dogwood. To know what plants need and when they need it, is paramount to your gardens overall maintenance program, health and appearance.

Here are few more winter pruning hints. Orchard trees are hardy as a rule, and can be pruned anytime after your New Year’s Eve party, but before Easter. Apples, cherries and pears can take a hard pruning in cold weather. Peaches, on the other hand, can be a bit more delicate. I like to wait until the threat of sub-zero weather has past. Fresh cuts on peach trees can be wounded by rapid temperature variations, causing possible dieback during the approaching growing season. Evergreen shrubs can suffer the same damage if pruned too early in winter. Boxwood, Japanese holly, yews and others are best pruned in late winter/early spring. This is a good point at which to make a comment about timing.

All of us know that evergreen plants make beautiful and festive Christmas décor. Asking you not to prune evergreens until late winter makes this a bit difficult. The truth of the matter is this. You can prune plants in the wrong season as long as we practice restraint, and are not concerned about losing flowers. Rather than taking a great deal of green material from one part of the plant, take small pieces from the plant’s total area. This will leave small protected holes in the plant rather than a large exposed section. When the correct season arrives, continue your efforts on a grander scale. In our area, due to unpredictable weather, I would only do light pruning in fall. We sometimes cut hollies hard during a renewal project. To leave them unprotected all winter may cause problems later in its life. When we naturalize prune, or open the plant to light, enhancing inner growth, we submit the plant to temperature fluctuations. Our Mid-Atlantic region can easily experience a daytime temperature in the 40’s and 50’s and in that same day have a night that is below zero. When opening boxwood and other plants to the warming sun, water can rise in the xylem during the day and freeze at night. Water of course, expands as a solid and can rupture wood cells, possibly causing pathogenic disruptions within the plant’s vascular system. These are places where canker causing fungi can take hold, physically harming the plant. Again, this is a situation over which we have complete control.

As artful pruners should continually ask ourselves, what are we doing to a particular plant, and how will our actions affect its health? Our plants reaction to our pruning will be clear and blatant. In our plant’s opinion, are we friend or foe? By waiting to prune until the threat of frigid weather has past but before growth begins, will assure a safer situation for our evergreens. Pruning plants late in winter allows them to remain “naked to the world” for as short a period as possible. This must be when Eric Burden prunes his plants. Opening or naturalizing plants allows them, through the power of sunlight, to grow leaves on their interior surfaces. Our goal is to help plants grow as many leaves as possible to insure adequate production of food, which only they can do for themselves. We cannot feed our plants. “Not a shrub or tree can be fed by me, but the sun shall have fun, turning leaves to tea”. I’m afraid our human powers are limited, compared to those of the sun, allowing us only to simulate or augment that which lies naturally on the forest floor.

A final word. Pruning a woody plant in the wrong season will affect flower production. On the other hand, I believe winter is a great time to prune any shrub for their health and well-being. We do this to renew plants when flowers can be sacrificed for a year. Always, the most important issue in pruning woody plants is that we make our cuts on each plant WHERE the individual tree or shrub dictates. Making a bad cut is worse for the plant than no cut at all. If you are not sure about a certain aspect of plant biology, ask your arborist or horticulturalist for help. Respecting branch collars and knowing plant physiology is the best thing we can do for our plants. So… this winter, dress up in that fashionable, layered look, holster those Felco pruners and prepare yourselves for the true joy of winter. As soon as I open my new pruning saw for Christmas, it’s outside for me so I can dive back into that hedge and become one with my shrubs! I’m just counting the days. Happy Holidays, (pruning)!!

Copyright 2005 by Peter Deahl. All rights reserved.

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