Pruning should not be considered a chore, but one’s expression of living art. There are numerous reasons to prune plants. From a grower’s perspective, we prune plants to train them to have full, well branched structures. Generally shrubs should be pruned every 6 to 8 inches, and trees are pruned every 12 to 15 inches. The result, on the one hand, will be a plant that has strong branches able to better withstand heavy snow and ice during the winter time. On the other hand, a well-pruned plant creates a work of beauty during the rest of the year.
Characteristics such as flower color, size, fragrance, leaf color during the season, or even fall color, will all be enhanced with proper pruning. The end result will allow you to produce a plant that will perform brilliantly for years to come. From a homeowners perspective, we prune plants to keep them from getting out of shape, growing too tall, too wide or more simply put, so they don’t cover up the windows, grow over the walkway, or up against the house. Whether you are a professional or a weekend gardener, pruning a plant should have the same results.
When to Prune
The best time to prune flowering shrubs is just after they finish flowering. Shrubs such as forsythia, viburnum, lilac, and some hydrangeas (macrophylla varieties) produce the following year’s flower buds just after their current year’s flowers cycle. So if a lilac flowers in mid-May and we prune it by mid-June, the shrub will branch out again and then set its flowers for next year. If we prune that same lilac in the fall (perhaps because it is overgrown from several years of neglect), though we will put the plant back into shape, we will also lose the following year’s flowers. Sometimes it is better to prune a plant at an off time of year in order to correct years of neglect. Evergreen shrubs such as rhododendron, azalea, Japanese andromeda, and mountain laurel should also be pruned in the same manor. As for all other evergreens that are not known to have a significant flower, boxwood, juniper, arborvitae, holly, yew and hemlock, these should be pruned once in late spring and touched up with a light second pruning in the fall.
When we talk about pruning pines, be it Austrian, mugho, Scotch, or white, all trees or shrubs in this family should be pruned while their shoots (candles) are actively growing. These plants react similarly to flowering shrubs. They set their buds for next year’s branches (not flowers) just after they push their spring growth. If you prune them in fall you will take off their branch buds for the following year. Not to worry, they will push new branches the year after. Lastly, all trees and shrubs that fall in the spruce and fir families are best pruned in late spring through the fall.
The bottom line is picking the proper plant for the proper location will allow us to grow the plant as it would naturally. Learning how to prune plants so that we maintain them in an area that is too small for them to grow in the first place can truly dampen our spirits as a gardener. So in the end, a well- placed plant becomes one we come to admire…a thing of beauty…living art.
How to Prune
My first principle of pruning is always cut back to another branch or bud and to cut back to healthy wood. When we clip the top off a branch, the energy will flow to the bud or branch just below the cut. The result will be buds breaking open and producing new shoots. Most times after the plant is pruned, we see it grow furiously. Over the years when trimming is done to the outer portion of the plant, the canopy becomes very dense. As sun light is restricted from getting to the interior of the plant, the inside dies out. We see this typically happen with yews. We shear them and shear them to the point where there is nothing on the inside and what remains is an old crusty looking green shrub on the outside.
This leads me to my second principle of pruning that I call thinning-out. If we take that old crusty yew and open up the dense canopy by taking out small sections, we will allow sun to get to the center of the plant again. In order to take out a small section, perhaps 3 inches in diameter, we need to prune out a branch (or branches) about 6 inches long. Though this will look like a hole in the plant up close, from afar it will be unnoticeable. The benefit to the plant is getting sun into the center. Fortunately yews will produce buds from the older wood in the interior of the plant. Once those larger branches receive sunlight, the buds in the center will break open and develop branches. These new branches will grow from the darker inside through the three inch openings you made and toward the sun.
This practice takes time and patience. It takes more time to thin each plant and open up the canopy, and it takes patience to let the plant grow out over time in order to rejuvenate it. Combining both principles allows us to maintain the size of our shrubs in a more natural way. We end up growing our plants from within and not just on the outside. Thinned-out shrubs grow more open. They don’t grow “out of control” because this pruning practice does not stimulate excessive new growth. Yews, hollies, and junipers are evergreen shrubs that can be maintained for years at a desired height and spread by thinning-out. Viburnum, euonymus, weigela, dogwood, privet and barberry are some common deciduous shrubs that will also benefit from this technique.
by Frances and Larry Grossman
Larry Grossman and his wife, Frances, are the owners of Grossman’s Country Nursery, Inc. located in Penfield. Tune in every Saturday morning from 10 to 11 a.m. for the WHAM Garden Show Live with Grossman’s Country Nursery on WHAM 1180 and join Larry and Frances Grossman as they bring garden enthusiasts new and old into the fun and rewarding world of gardening.