To cut or not to cut? is not the question, but when and how to prune is. The long-term health and beauty of your landscape depends on properly pruning trees and shrubs. Plants left to grow freely can overtake spaces, crowd walkways, and become an unsightly feature in the landscape. A new awareness of the importance of aesthetic pruning calls for the retirement of electric pruning shears and instead marries the science of horticulture with artful interpretation of plant forms.
The main principle in aesthetic pruning is that plants must be pruned to fit within the context of their environment to cultivate the plants essence. The essence of most species can be found in nature. Take time to observe mature plants and you will begin to notice how the trunks of trees are rarely perfectly straight as they have bent and twisted over time to seek sunlight. In a forest, the layers of vegetation exist in harmonious balance such that each plant receives the necessary nutrients and sunlight it requires. Shrubs, too, have natural forms, be it creeping, vase shape, cascading, or mounding. With that in mind, consider how you might replicate the patterns of nature in your garden.
Before you pick up clippers or a saw, it is important to think of pruning on a timeline that extends years into the future. What can you begin to remove today that will help change the form of the plant over time? The same is true for young, small plants. If you begin to develop their form at this stage, the mature plant will be a beautiful part of the landscape.
From a horticultural perspective, pruning is quintessential to plant health, flowering, and fruiting. Spring flowering shrubs, such as lilacs, dogwoods, and viburnums, are pruned in late spring because they set their flower buds for the following year just after blooming. Most other deciduous trees can be pruned from mid-February until early May. Evergreens, with the exception of pines, can be pruned either prior to spring growth or during their dormant period in mid-summer. Pines should be pruned as new growth (candles) emerges in the spring.
Pruning is an important way to promote plant health. With all species, remove dead, diseased, and damaged branches. To ensure a healthy cut, remove branches as close to the base of a larger branch as possible. Doing so allows the plant to callus over the wounds and prevents the appearance of stumps. Renewal pruning is important for multi-stem species to eliminate old, declining branches, and can be done at any time of year by removing one third of the oldest stems to ground level.
Shaping and Thinning
All plants have a natural form and mature size. Shaping and thinning can enhance these natural forms, but it is important to choose plants appropriate for the environment. Environment, in this sense, includes horticultural principals of light, shade, and health, but also design principles of scale, texture, and form.
Shearing is appropriate for formal plantings; otherwise, plants should be shaped and thinned to display their natural form. When shearing evergreens, it is easy to create heavy mats of needles at the ends of branches or to take branches back to the inner dead-zone from which nothing will grow. Shearing deciduous species causes unnaturally dense growth at the ends of branches. Ideally, plants should be thinned by removing small, individual twigs back to the larger stem. In this way, thinning allows plants to display their natural essence without appearing pruned.
With its origins in Japanese gardening, aesthetic pruning allows plants to be shaped over time to enhance their natural form while creating harmony and unity in the landscape. The challenge to this type of pruning is that every plant is different and must be approached as an individual. Properly done, pruning will invigorate your plants and enhance the aesthetics and health of your landscape. A garden is not stagnant, but constantly developing, and so, too, must pruning.
Joan W. Ziegler is a horticulturist and garden designer and winner of the 2015 Perennial Plant Association Merit Award for Residential Landscape Design, and Lily Mank is an intern landscape architect for ZDA, Inc. Landscape Architecture, 4797 Capitol View Road, Middleton. Call (608) 831-5098 or visit zdainc.com . Photographs provided by ZDA, Inc.