How to Prune Evergreens and Conifers
Find out how pruning creates consistent texture and appearance in conifers, while encouraging healthier growth in the long run.
There is a different concept of pruning, called Aesthetic Pruning. My Aesthetic Pruning definition is: controlling plant growth in a way which results in plants which look convincingly natural and untouched by human hands.
The gardener must have two arsenals of knowledge: the growth habit of the plant and the use of proper pruning tools. The reference I use is Edward Gilman’s 2012 book, An Illustrated Guide to Pruning (Third Edition), Chapters 5 and 18, Pruning Cuts, and in Pruning Landscape Trees and Shrubs, published by Delmar Cengage Learning.
There are three basic pruning terms that I will discuss:
- Reduction Cuts
- Removal Cuts
- Heading Cuts
These are two additional cuts to be used:
Defining Pruning Terms
Reduction Cuts are used to “reduce” or shorten the length of a branch by pruning it back to a branch junction which is large enough to assume apical dominance. This branch varies by species, but should be 1/3 to 1/2 the diameter of the cut stem. To make the cut, bisect the angle between the branch bark ridge and an imaginary line perpendicular to the branch to be removed. This cut is used to maintain the size and shape of the tree or shrub.
Removal Cuts are made back to the collar, or to the point of attachment. This cut is often used to thin-out the plant’s foliage. This encourages light and air circulation resulting in a healthier specimen. Removal cuts can be used to lighten the weight of branches and removal of dead wood.
Heading Cuts shorten a branch to a stub or to a bud or a lateral branch not large enough to assume the terminal role. This can cause the tree to sprout excessively from the cut.
Other Pruning Techniques in Conifers: Tipping
Tipping/pinching is a technique of removing the last few buds, leaves, or sprouts from the end of a stem. It is performed for a number of reasons. It can slow down a tree’s rapid growth; it can redirect a tree’s energy into smaller, more desirable shoots or buds, and it can give a consistent texture and appearance to the newly pruned plant.
Tipping is easiest during the soft-lush-growth stage by using the fingers. For pines, breaking the new growth candles to the desired length before hardening controls the total yearly growth. The use of hand shears for removals must be done on new growth after it has hardened, which can cause browning of foliage and needles.
Other Pruning Techniques in Conifers: Shearing
The overuse and misuse of sheared shrubbery is one of the most common forms of landscape mismanagement. Because shearing is non-selective heading, you will stimulate bushy growth. You create a twiggy outer shell on sheared plants. This layer of twigs shades out the interior, which then becomes leafless and full of dead leaves and dead wood.
Meanwhile the outer shell becomes thicker and larger farther out to retain its greenery. The dense outer shell makes size reduction difficult because cutting back too far exposes the ugly dead zone. Although most plants will bud back and eventually reform, there are some species like junipers which won’t regenerate.
Power hedge shears do tremendous damage with [lots of] broken and crushed stem tips, torn bark and chewed leaves. This leads to wound responses and both bacterial and fungal invasions.
Alternatives to Shearing in Conifers
The only plants I shear are Boxwood and Privet, using manual hedge shears held in the horizontal position. This is because they have small leaves and are formal in appearance. The highest quality “shearing” isn’t even shearing at all. Instead it consists of the carefully performed “snip-by-snip” technique, which leaves no heading cuts at all; the manual head shears are held in an vertical or right angle position for “targeted” cuts on junipers, barberries, Spiraea, hemlocks and many more species with follow up use of hand shears for fine pruning removals.
Targeting cuts to inner branchlets opens up the plant to let in more light and air circulation, allows new growth to emerge from buds or side branches, and controls plant size. I prefer that certain shrubs be pruned in a semi-spherical and not a ball-like shape.
The preferred ratio of height to width is 1 to 3. This allows the entire bush to have new foliage or flowers and appear ground-hugging. Many shrubs with sheared tops have exposed sides which have little new foliage and the shape is of little interest.
Things to Consider Before Pruning
- What does the tree or shrub look like in nature in its most mature form?
- Find examples in the landscape as you drive down the street and in books and garden magazines!
- Check branch forms: hanging or upright shapes?
- Observe ratio of height to width to inform your pruning goals!
- Where are the empty spaces between branches and note branching pattern?
Information selected from The Journal of Japanese Gardening, published by Douglas M. Roth, Plant Amnesty Newsletter, www.plantamesty.org.
Photograph by David Rangel.
This article was originally published in the Fall 2014 issue of Conifer Quarterly. Join the American Conifer Society to access our extensive library of conifer-related articles and connect to a nationwide group of plant lovers! Become a member for only $40 a year and get discounts with our growing list of participating nurseries in our Nursery Discount Program.