A Time to Prune
By Mike Lang
Have you ever caught yourself peering through the window on a sunny winter’s day yearning for a more meaningful task in the garden than filling the bird feeder? The ground is frozen, so working the soil in the vegetable garden is out of the question. Leaves that have gathered in perennial beds insulate the shallow rooted plants from the rest of the season’s cold and are best left in place. What is a gardener to do?
Prune, prune, prune.
The task of trimming trees and shaping shrubs is often completed in winter because the plants are dormant, and, in the case of deciduous species, leafless. This allows you to take care of business in a season when there are few other things to do, instead of when everything is growing at what seems like a hundred miles per hour. It also makes the job easier because formerly foliage-covered problems can be detected more readily.
Understanding your plants is the most important part of dormant pruning, or any pruning for that matter. If you have a blooming shrub, know when it blooms. Spring bloomers, such as forsythia, lilac and quince, produce flower buds on the previous season’s growth. Pruning these plants now will remove flowers that are poised to appear in the coming weeks. But the process won’t hurt the plant, and it might be wise to do some shaping, if the specimen has grown too large for its location. Summer-blooming shrubs like crape myrtle and dwarf spirea develop flower buds on the new growth of the season, so a winter haircut will actually promote more blossoms for the coming season.
It is wise to avoid pruning more tender shrubs until you are sure that winter’s chill has passed. Shrub roses are one of the plants that I would group as tender. Even though they come through the winter in excellent fashion, an early winter pruning can result in some damage at the cut. It really doesn’t harm the plant, but you will need to prune out the resulting dead and damaged stems later, which isn’t very productive.
Dormant pruning of landscape trees is a must in my garden. With the foliage absent, I can give the plant’s structure a good inspection and easily identify deficiencies. I have heard from some gardeners that it is hard for them to prune without the foliage because they cannot picture how the tree will look without the leaves. My standard reply: “If you were building a house, wouldn’t you want to inspect the structure, and make changes before the siding goes on?”
Problems to look for when pruning landscape trees include: damaged and diseased wood, rubbing branches and other growth that would be detrimental to future development.
The cardinal rule for pruning landscape trees is to remove no more than 1/3 of the canopy at one time. Over-aggressive pruning will cause numerous fast-growing sprouts to grow. These new limbs are often weakly attached, have poor strength and cause long-term structural problems. This phenomenon is often seen in trees below power lines that are routinely topped.
Generally, any of our landscape trees can be pruned during the dormant season. Don’t worry about pruning a spring-blooming species like magnolia, pear or crabapple; the benefit of cutting them back far outweighs the loss of a few blooms. A few tree species such as maple, birch, mulberry and Osage orange will bleed sap if pruning takes place in late winter. Although it’s unsightly, sap leakage is not detrimental to the tree.
Late-winter pruning of fruit trees is imperative, whether you have a newly planted orchard or have inherited some overgrown, neglected trees with the purchase of a property. Careful cutting will make the trees look nice, but it is even more important to promote good yields of high-quality fruit. It is critical to remove diseased and damaged limbs from fruit trees to avoid spreading the pathogen and giving it a place to take hold.
When pruning fruit trees, be sure to remove rubbing branches and other unfocused growth; work toward opening up the canopy to increase sunlight penetration. Trees with dense canopies will tend to produce fruit on the perimeter. Inner branches can have good fruiting buds, or spurs available for production, but sufficient energy isn’t available because of the lack of sunlight for photosynthesis. A dense canopy with branches growing too close together will also cause the fruit to be small.
In general, fruit trees should not be pruned as heavily as landscape trees. If your goal is to rejuvenate an overgrown tree, prune it over the course of three or four years. Pears and apples in particular will respond with a flush of vigorous growth (water sprouts) when pruned aggressively. These sprouts will not produce fruit and only will detract from the overall health of the plant.
In the past, sealing the tree’s pruning wounds with tar, paint or some other coating was recommended (to keep disease out and to aid in healing), but that’s no longer the case. Sealers have been found to promote disease and inhibit healing in many species. My recommendation is to avoid sealers altogether and let the tree’s healing mechanism proceed unimpeded.
The next time you yearn to work in the yard this winter, why not clean up the pruners, spend a few minutes with the sharpening stone to give them a fresh edge and get to work on the pruning? It will be a welcome relief from the house or shop, and pay off for seasons to come.
Mike Lang is a lifelong Kansan, and he is currently the landscape manager for a 1,000-acre university campus by day and caretaker of his own quarter-acre piece of the world the rest of the time.
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