Pruning tools in the hands of untrained gardeners can be implements of damage and destruction to the trees and shrubs in our gardens.
We’re entering the prime pruning season, so it’s a great time to point out the pitfalls in the hopes that I can help you avoid them.
- Prune with a purpose. Never prune “just to be pruning.” Don’t assume that any plant has to be trimmed. The guidelines are simple and they’re easily noted. Read up on them beforehand. Addressing timing of pruning, plants that should be trimmed during the winter dormant season include shade trees, evergreen shrubs, peach and plum trees, grape vines, summer-flowering shrubs and vines and, in early February, bush roses.
- Wait to prune spring-flowering shrubs and vines until immediately after they finish blooming. Wait to prune blackberries until immediately after harvest, and then cut all canes that bore fruit completely to the ground. Dead wood can be trimmed out of trees and shrubs at any time. If you intend to scalp your lawn, that should be done around March 1.
- Leave no stubs as you prune to remove branches. They will not heal properly and decay will set in. Over ensuing years, that decay will move into the main trunk and you will end up losing the entire tree.
The correct way, instead, is to leave a very small piece of the branch “collar” intact. That’s the swollen base of the branch where it attaches to the trunk – like the “delta” of a river where it flows into an ocean. That collar will normally be only 1/8- to 1/4-inch in thickness. A roll of new bark will grow across the cut surface. If there’s a stub, there’s no way for it to do so.
Pruning sealant should be applied to all cuts made to oaks to protect against invasion of oak wilt, but other species should be left to heal on their own.
- Avoid pruning plants into squares, globes or other unnatural forms. I know I’m out on thin ice here, but I’ll creep out a little farther. The landscapes that are generally most pleasing to the eye are usually built along natural curves and groupings. Long, straight rows seldom show up in nature, and when they do it’s usually because birds have “planted” seeds as they sat on old fencerows.
Whenever you can, lay your beds out in long, graceful sweeps, and plant your shrubs in clusters of odd numbers of plants. Unless you have a very formal garden design, you’ll rarely need hedge trimmers at all.
- Don’t “top” your crape myrtles. If you read my column with any kind of frequency you knew I’d be including that topic under the umbrella of “pruning mistakes.” It’s one of the worst. I don’t believe I’ve ever brought it up this early in the winter, however. I decided this might be a good time to do so, before the commercial landscaping companies start assigning that job to their crews right after the holidays. Topping is really bad business. It ruins the plants’ shapes, plus it delays blooming by six to eight weeks the following summer. It does nothing to reduce the plant’s height – it grows right back to where it was. My feeling is, if you have a crape myrtle that’s too large for its spot, “either move it or remove it.”
- If you need to reshape overgrown evergreen shrubs, do so carefully. Sometimes we end up with shrubs that have either grown up over windows or that have been pruned enough times that they’ve lost most of their lower growth. In those cases you might try trimming them back by 25 to 35 percent toward the end of the winter to see if they have the vigor to put out new growth in the spring. That works with hollies, boxwoods and abelias, but don’t try it with junipers. They don’t have the dormant buds they would need to develop new shoots.
- Nandinas have their own rules for pruning. When they grow taller than you want them to be you trim them cane-by-cane with lopping shears. Remove the tallest canes clear to the ground. New shoots will sprout out from the bases and fill in so that the plants won’t appear leggy. The following January you would do the same thing, removing another set of tall canes. Generally, we do that to one-third or one-half of the canes each winter. Or, put in simpler words, never cut a nandina stem halfway to the ground.
And, while you’re at it, do this pruning before the cedar waxwings migrate back to the north in late winter. They flock through the nandinas eating all of their berries. Their stomachs can’t process them properly, however, and the birds can get sick and die.
- You may need to prune roots that are becoming a hazard. There are times when roots grow along the surface of the ground. In those instances, it’s common for them to become risks for tripping. Some roots can grow large enough to crack foundations, break pipes and cause driveways and walks to heave. In all those cases you may want to prune to remove them, and winter is the best time to do so. Covering them with soil is never a solution, as they will simply grow up and through the new soil, too.
Finally, one last suggestion relative to pruning large trees: They represent a significant investment in time and value. Have an International Society of Arboriculture Certified Arborist oversee major tree work for you. It’s an investment you can’t afford to pass up.