To learn more
For more about good pruning techniques and what tools to use, visit this Virginia Cooperative Extension Web page on pruning.
Adam Downing also recommends the book “An Illustrated Guide to Pruning” by Ed Gilman and “Best Management Practices Series (BMP) — Tree Pruning,” an International Society of Arboriculture publication available here.
“Off with their heads” is not a good idea when pruning.
I cringe when I have to trim my dog’s nails. She has black ones, so it’s pretty much impossible to know just where the nerve that runs through each ends. I tend to be really cautious and clip very little — probably less than I should. I approach plant pruning with as much apprehension — even more, since I know less about plants.
Having moved around all my life, I haven’t had much reason to get involved with pruning. However, the landscaping at the house I’m now renting is a case study in bad pruning, so I thought that maybe it was time to learn more about possible remedies. Adam Downing, a Virginia Cooperative Extension agent working in the Forestry and Natural Resources division, was giving a talk on pruning sponsored by the Rappahannock County Garden Club, so I attended.
According to Downing, there are six reasons to prune: improve the appearance or health of a plant, to control the size of a plant, to prevent personal injury or property damage, to train young plants, to influence fruiting and flowering, and to rejuvenate old trees and shrubs.
In pruning a plant, you become involved intimately with its growth and health. You’re basically forcing a plant to grow the way you want it to grow, not necessarily how it would grow if left alone. This interference in the plant’s life can thwart healthy growth or support it, depending on the approach you take. As Downing pointed out, understanding the biology of normal plant growth and when, where, and how to prune — and what tools to use — are the keys to success.
One of the most important things to understand is the role of dominant branches and the terminal buds at their tips. These buds release auxin, a hormone that controls shoot length and inhibits growth of lateral buds. Cut off the terminal bud, and the little guys take over, sprouting out vigorously. This can diminish the health of the plant, making it spread its resources thin throughout all the lateral branches rather than focusing on a few dominant branches. It also invariably leads to an overly bushy, uneven, bad-haircut appearance that’s difficult and time-consuming to correct. The best way to avoid a plant’s growing too tall is to nip that problem in the bud figuratively, rather than literally.
The process of picking a puppy and picking a tree or shrub can present the same hazards. How many times do people pick that cute little puppy, not realizing it will grow into a 100-pound monster that will take over their house? Similarly, that sweet little shrub in the nursery may grow far beyond the space in which it is to be planted.
The response to this is often “topping” the plant — arbitrarily cutting off the trunk and surrounding dominant and lateral branches — which can shorten its life as well as actually spur growth. The topping cut wounds the plant, encouraging disease and insect infestation, and, as Downing pointed out, applications of any of the various wound treatments commercially available don’t help.
When trees and shrubs lose branches, they have a system that helps them survive such losses, sealing off the wound physically and chemically. “Animal wounds heal, plant wounds seal,” as the arboriculturist’s mantra goes. In fact, losing some lower branches is part of the natural growth process for many trees. However, healthy plants rarely have to deal with nature slicing off their tops, so it’s harder for them to heal such a brutal cut.
It’s a lot better to pick the right plant and manage its growth carefully from the start than to try to correct problems later. And if you care about wildlife and the health of our ecosystems, natives are best. They often generally do fine with little care, if you pick the right plant to begin with.
Three holly bushes that were included in the foundation plantings for the house I’m renting were not picked carefully for their growth habit, and several are now competing with the gutters for vertical space. Years ago someone apparently decided to solve the problem by topping them. Above the cuts, the bad-haircut effect is glaring — a bushy, dense sprouting of many small branches that themselves now have small branches, the topmost of which are basically growing straight up into and beyond the gutters. While there are ways to rehabilitate this barbarous pruning attack, it will take a lot of time, fortitude, and skill — more than I have.
Pruning is a complex topic, and as much art as science. Although we often treat plants in our yards as mere decoration, the more we learn about their lives, their complexity, and their role in the larger ecosystem, the more likely we are to appreciate and treat them as living things trying to find their place in the natural world, just as we are. The reward for us is a healthy, aesthetically pleasing landscape.