Turn Overgrown Shrubs into “Trees”

A small shrub that you brought home from the nursery has grown into a towering monstrosity that threatens to take over your entire front lawn. What should you do? You have two basic options: remove the plant or prune it. Depending on the species, you may find an attractive tree-like shrub beneath the tangle of overgrown branches. In fact, careful pruning may create a beautiful centerpiece in your garden. Although any shrub can be trimmed, the following are particularly well suited to being transformed into attractive small trees and some produce a bounty of flowers: 

  • Azalea
  • Chaste tree
  • Rhododendron
  • Rose-of-Sharon
  • Viburnum
  • Waxleaf privet
  • Wax myrtle
  • Winged Euonymus
  • Burford holly

Pruning

Improper pruning can cause damage to the plant and leave it susceptible to disease. Most plants when cut or otherwise injured will ooze resin from the damaged area. Resin is the plant’s way of protecting itself; the resin hardens and prevents fungus and insects from entering the plant surface. To give you some idea of the hardness and durability of resin, amber is ancient resin, which has crystallized over time.

When pruning, it is important to work with the plant’s natural self-defense system. Do not cut branches flush with the trunk instead, cut one to two centimeters away from the trunk, just outside of the branch collar. This is the raised area at the base of the branch where the branch joins the trunk. The collars on the branches of most trees and shrubs appear as a knob of concentric rings of bark. A plant will heal more rapidly and eventually form a bark ‘scab’ over the wound if you cut just outside of the collar. 

When trimming branches larger than four centimeters in diameter or branches heavy with leaves, a single cut could damage the trunk. As you saw through a heavy branch, it begins to bend toward the ground. As you continue sawing, greater pressure is applied to point at which the branch joins the trunk. As a result, the falling branch may rip the bark. In order to avoid unnecessary damage to the plant, you should make two cuts. The first cut should be approximately 20cm from the trunk. This eliminates much of the weight of the branch without damage to the trunk. Next, trim the rest of the branch by cutting just outside of the collar.

Remember, insects and diseases can be passed from one plant to another from pruning shears and saws. Once you have finished working on one plant, clean your tools with rubbing alcohol or gasoline before moving onto the next. Avoid pruning the day before the forecast calls for rain. The open cuts will be susceptible to the molds and fungus carried by the rain. A few dry days will allow the resin to dry and form a seal.

Where to Prune

Before you begin trimming, take a look at the trunk and branch formations of trees. You will notice that the lower trunk is typically bare without any small branches. Higher up, you will find the trunk splits into two or three sections. Yet higher, those two or three branch sections divide into more sections and so on. The greatest mass of leaves is on the top half of the tree. 

An overgrown shrub will likely have a mass of leaves extending from the top to the bottom of the plant. The effect is an unruly mass of vegetation. At several metres tall such as plant can become the main (an unwelcome) focal point of your yard! 

The first step in making this type of shrub resemble a tree is to trim the small branches from the main trunk. As a general rule, the bottom quarter of the shrub should be cleared of small branches leaving the main limbs exposed.

Many types of shrubs do not have a solitary limb forming the trunk instead it is comprised of a few large limbs. This makes pruning more challenging. Carefully trim the small branches working from the outside in so you can see where you are cutting. Once you have trimmed all of the small branches from the bottom quarter of the shrub, the main limbs should be clearly visible.

At this point you may notice a stark difference between the bottom quarter and the rest of the tree. Although the bottom quarter is bare, the rest of the shrub is thick with leaves. Next, selectively trim branches to create a gradual transition between bare and leafy sections. Step back and assess the progress at regular intervals to avoid cutting too much.

Lastly, you have arrived at the top half of the shrub. Use a sturdy ladder and ask someone to hold it steady as you trim the upper branches. You may wish to prune to reduce height but keep in mind that it will be an annual maintenance task. In Canada, flowering shrubs typically bloom once a year so pruning will not stimulate a second flush of blooms. You may, however, wish to prune in order to shape your shrub.

Two common tree shapes are round (like topiary) and gently curved. Curved refers to a slight concave curve on the underside of the tree. In order to achieve the look, trim the top of the shrub and allow the side branches to grow longer – they will dip slightly creating a curve.

Now that you have tamed your overgrown shrub, you can enjoy a new sunny patch of earth for flowers not to mention a stunning new “tree” in your garden.

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