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Monday, April 22, 2024
Growing Together: Pruning deciduous shrubs to be a cut above the rest
Joanne Young says to prune one-third of the oldest growth from your shrubs. (JOANNE YOUNG)

To help understand pruning a bit better, last week we looked at some of the science about how a plant grows.

This week, here are some tips on pruning deciduous shrubs.

In general, the best time to prune any deciduous woody plant is just before the new growth starts in spring (the late dormant period from March to mid-April). 

Pruning at other times can rob the plant of stored food and energy. It may also mean a loss of flowers or fruit. With that said, all rules has some exceptions. Here are those exceptions:

  1.  Any early spring flowering plants (plants that bloom off old wood) should be pruned immediately after flowering and before leaves unfold. Some examples of these plants are magnolia, forsythia, wisteria, serviceberry, lilac, quince, bridal wreath spirea, most Viburnums.
  2. Trees such as maples (including Japanese maples), flowering Dogwoods, birch and elm will bleed if pruned in late winter or early spring.  A better time to prune these trees would be mid-summer.

Let’s be honest: how many of your shrubs have the same shape after you have pruned them? Chances are once the plants have been in your garden for a couple years, they all start looking the same. 

When pruning deciduous trees and shrubs, many people will just shear back the top of the plant to reduce its overall height, but this is only one part of proper pruning techniques.  Here are some steps to follow.

Step 1. When pruning any shrub or tree, always start out with the 3 Ds of pruning. That means you prune out any dead, diseased or damaged branches first.  

Step 2. Next, remove any branches that closely cross with other branches or that cross through the middle of the plant. You want to have branches that come from the centre of the plant and head outward.

Step 3. 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. There are four main goals of pruning that you should consider before you begin:

Control plant size: The best way to do this is by natural pruning which means making selective cuts to thin or reduce the overall size of the plant. 

You are not just shearing off the tips but removing branches using secateurs or loppers.  When you only shear back the tips, your shrubs will become very wide at the top because of this increased branching, giving it an ice cream cone-like appearance. 

When 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. When pruning is completed, the plant should still have its natural form.

Increase quantity of flowers and fruit: Proper pruning will aid in the production of flowers. 

Most flowers are produced on the tips of the stems, so the more tips there are, the more flowers you have and the more fruit that will be produced. 

To accomplish, cut back the stem tips, stimulating the side branches and developing more tips for the flowers to form on. Just remember, the more flowers a plant produces the smaller the flowers will be.   

Maintain a certain shape: 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 just remove new tip growth, creating a full dense look.  Even though electric shears make the job easier, hand shears do a much nicer job of things. 

Electric shears tear the plant tissue while hand shears make a cleaner cut. When the plant tissue is torn there is more die back at the tips, giving the sheared shrub a brownish tinge.

Prevent this by making any pruning tool is sharp and clean before using it.

Rejuvenate an older shrub: We tend to let shrubs grow year after year and once they become too large, we hack (not a proper horticultural term) them back, hoping 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. 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. That will stimulate growth from lower down. In three years, you will have completely rejuvenated the shrub.  

Keep these tips and goals in mind as you tackle your garden this spring and you will be a cut above the rest.

Joanne Young is a Niagara-on-the-Lake garden expert and coach. See her website at joanneyoung.ca.


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