Pruning may seem to be a mystical process, carried out only by gardeners with magical knowledge and power. It’s not – some guidance and practice is all that is needed. Nature is quite forgiving and it’s rare that a novice gardener will kill a shrub through pruning.
Keep in mind that planting the right shrub in the right place will ensure the health of your plant. Healthy plants require less human intervention. Sometimes we inherit neglected plants in awkward spots and then it’s time to take out the pruners.
Reasons to Prune
1. Health and appearance of the plant: removing dead, diseased, dying or damaged parts. Removing crossed limbs prevents damage from rubbing.
2. Safety: removing dangerous limbs covering walkways, gates, windows or doorways.
3. Shaping shrubs: This depends on your perspective about nature. Some of us prefer a natural look, while others want their shrubs to be in particular shapes – round, square, etc. Shrubs in natural shapes require less maintenance than those in an unnatural shape.
4. Pruning to encourage blooms, fruit, or to encourage a plant to be more leafy and dense.
5. Pruning to prevent shrubs from shading out or overtaking other plants.
Tools
Secateurs, sometimes called simply “pruners”; pruning saws, straight or curved blades; long-armed pruner to reach tops of tall hedges; hand shears; power hedge trimmer — all have their uses.
All your tools need to be sharp so that cuts are as clean as possible. They also need to be cleaned regularly, particularly when cutting out diseased limbs. Dirty tools can spread disease throughout your garden.
Regular cleaning can be done with soap and water, removing rust with steel wool, then drying each tool carefully. Disinfecting tools after cutting out diseased plant material needs to be done right after use, before moving on to another plant. Pruning is beneficial for plants, but it also wounds them. An open wound can allow blight, powdery mildew, and bacteria to infect the plants.
Rubbing alcohol (70%) or hydrogen peroxide on a clean cloth are both easy and cost-effective options. A wipe with either immediately kills most plant pathogens, with the exception of apple trees with fireblight. After sanitizing, be sure to dry the tools thoroughly.
Multi-stemmed Shrubs
Most flowering shrubs will bloom either on 1-year-old growth, or on new growth.
Plants that flower in the spring bloom on the previous season’s growth. Prune these soon after flowering during active growth. Examples: Serviceberry, Forsythia, Redbud.
Late flowering shrubs bloom on wood produced in the current season. They should be pruned when dormant in later winter to promote growth in spring. Prune before bud break. Examples: Snowberry, St John’s Wort, Elderberry.
Plants grow from their tips, stimulated by growth hormones called ‘auxins’. Sap carries the auxins through the rest of the plant. Trimming the tips of shrubs will result in a bushier, denser plant. Keep this in mind when trimming a hedge. You can trim a shrub into the desired shape to fit your aesthetic sense and to fit into its environment.
Each year remove dead material and very old branches as near to the ground as possible. This will rejuvenate the shrub. Don’t remove more than 1/3 of the plant at any one time.
Pruning Evergreens
Evergreen trees and shrubs have either narrow- or broad-leaved foliage. Most are conifers and have either needle or scale leaves. Narrow-leaved evergreen shrubs commonly planted around the home include yew, juniper, arborvitae (cedar), and false cypress. Broad-leaved evergreens are represented by rhododendron, holly, and boxwoods.
For a hedge with an even height, prune the tip of the shortest plant by 1/10 of its height and then prune all others down to this height. Pruning off the tops will encourage the trees to fill out and will result in a thicker hedge. Always prune a hedge slightly narrower on top to allow even light penetration and prevent snowfall damage.
Be cautious about planting Boxwoods. Read about the problems with them here: Boxwoods: A Changing Landscape
To avoid problems with hedging plants and all shrubs, it is best to choose species native to your region. To find suggestions and reasons to plant native, follow this link: Gardening with Native Shrubs: A Toronto Master Gardener’s Guide
Junipers
Junipers’ new growth emerges from the tips, and they never produce new growth from lower on the stems. If you cut into a bare spot, it will remain bare for the juniper’s lifetime. Cut out dead or unwanted from below so that an upper branch covers it. This is particularly effective with creeping, low growing types.
Cedar
Cutting into a dead area of cedar will never produce new growth, so do not prune past the green, growing section. Pruners or loppers will give clean, even cuts.
Yew
This evergreen can be pruned any time of the year. Trimming will stimulate a full, healthy look in a hedge or stand-alone shrub.
Pruning Conifers
Since pine and spruce trees are not recommended to plant near homes and other buildings, they should be allowed to grow naturally in a space large enough for them to reach maturity. They seldom need pruning, except to remove dead or diseased branches. Pruning pine or spruce candles (the tender, new spring growth) can be done in late spring to control size and increase density. Simply pinch or cut off 30% to 50% of the new shoots before the needles expand fully. This works particularly well with dwarf forms of pine and spruce.
If you have a particular gardening question, you can leave a message on our contact page, or email Tri-County Master Gardeners at tricountymgs@gmail.com.
Helpful Links
How to Properly Prune Deciduous Shrubs
REFERENCES
Perfect Pruning a Practical Guide by Simon Akeroyd. National Trust Books, London, U.K. 2019
How to Prune Trees, Shrubs and Climbers by Richard Bird. Lorenz Books, London, U.K. 2015
Submitted by Leslye Glover, Tri-County Master Gardener
