PRUNING DECIDUOUS SHRUBS
To prune or not to prune? That is one of the most often asked questions. One of the first chores that we attack in our gardens each spring is pruning, but I find that most people are not quite sure what it is that they are supposed to do. Knowing the proper pruning times and proper pruning techniques seem to be the most misunderstood areas of gardening. Pruning promotes flowering, reduces pests and contributes to the plant’s overall health, all while helping it maintain an attractive shape. The longevity of a plant, its productivity and the overall health of a plant is mainly determined by how well it has been pruned over the years, so it is very important to know and understand the proper way to prune your shrubs.
When To Prune
In general, the best time to prune most deciduous woody plants is just before the new growth starts in the spring or, in other words, late dormant period (early March to mid -April). Pruning at other times can rob the plant of its stored food and energy. It may also mean a loss of flowers or fruit.
With that said, all rules have some exceptions. Here are those exceptions:
- Any early spring flowering plants (plants that bloom off old wood) should be pruned immediately after flowering and before leaves unfold. These are some plants that this exception applies to: Magnolia, Forsythia, Wisteria, Serviceberry, Lilac, Quince, Bridal Wreath Spirea, Viburnums, Serviceberry and Wisteria
- Trees such as Maples (including Japanese Maples), Flowering Dogwoods, Birch and Elm, Poplar, Laburnum and Lindens will bleed if pruned in late winter or early spring. A better time to prune these trees would be mid-summer to early fall.
Where To Start – THE 3 D’s OF PRUNING
Many people, when pruning deciduous trees and shrubs, will just shear back the top of the plant to reduce the overall height of the plant, but this is only a part of proper pruning techniques. So what else is involved in pruning? What steps should be taken when starting to prune?
Step 2. Remove any branches that closely cross with other branches or that cross through the middles of the plant. You want to have branches that come from the center of the plant and heads outward.
Step 3. The next step is to consider your pruning goal. Read below to discover your goal.
How To Prune – Knowing Your Pruning Goal
When pruning any plant, it is always good to know what your goal is and that will help you determine how to best prune your shrub. Here are the 5 main goals of pruning and the questions that you should be asking yourself before you begin:
The best way to control the size of a plant is by natural pruning. Natural pruning means that you are making selective cuts in order to thin or reduce the overall size of the plant. This cannot be done with shears, but with secateurs or loppers. It means cutting one stem at a time and not just shearing off the tips. When all you do is shear back the tips, the plant loses its natural form because it increases the number of branches and creates a branch structure that resembles a candelabra. Your shrubs will become very wide at the top because of this increased branching, giving your shrub an ice cream cone-like appearance. And because the top is so wide, it stops the sunlight from hitting the base of the plant and you are left with a plant that is bare at the base. Always prune back to a point just above a side shoot or back to just above a bud. When pruning is completed it should look like no cuts have been made. It should still have its natural form.
GOAL 2 – Increase the Amount of Flowers and Fruit
Proper pruning will aid in the production of more flowers and more flowers produce more fruit. Most flowers are produced on the tips of the stems, therefore, the more tips that there are, the more flowers that the plant will produce and the more flowers you have the fruit will be produced. In order to accomplish this goal, you cut back the stem tips, stimulating the side branches and developing more tips for the flowers to form on. Just remember that the more flowers that a plant produces the smaller the flowers will be. Fewer flowers usually mean larger flowers.
One of the goals of pruning might be to maintain a certain shape such as a hedge, a globe form, or specimen plants like spirals and pompons. This is best achieved by shearing. With shearing you are just removing new tip growth, creating a full dense look. Even though electric shears makes the job easier, hand shears make a much nicer job of things. Electric shears just tear the plant tissue while hand shears makes a cleaner cut. When the plant tissue is torn there is more die back at the tips giving the sheared shrub a brownish tinge. Always make sure that any pruning tool is sharp and clean before using to prevent this from happening.
GOAL 4 – Encourage Colourful Bark
There are certain plants, such as red or yellow twig Dogwoods and Japanese Kerria, which have colourful bark. In order to keep the colours as intense as possible special pruning is required. It is the youngest stems that will give you the brightest colour. As the stems age, they start to lose their colour. So the best way to encourage colourful bark is by pruning out (right to the ground) one third of the oldest growth every year. You will be able to tell which ones are the oldest stems because they will be thicker and more grayish/brown in colour. This encourages new growth to come up from the base, which will then give you more colourful bark.
In most cases, we tend to let shrubs grow and grow and once they become too large, we hack them back hoping that they will survive and become beautiful again. It is much easier to do a bit of pruning every year than to wait until the shrub is out of control. It is sometimes very hard to rejuvenate an old shrub that has been ignored for too long. The best way to rejuvenate an old flowering shrub is to do so over a three-year period. This can be achieved by removing one third of the oldest growth every year right back to the base, which will then stimulate growth to come from lower down. In three years you will have completely rejuvenated the entire shrub. With some flowering shrubs you can drastically cut the stems back to about 4”-6” above the ground. It may look funny for that season, but it will fill back in eventually.
I hope that this helps you to tackle your pruning chores this spring. Happy pruning!