As we near spring, these next few weeks are ideal for pruning landscape trees and shrubs.
The rule of thumb when pruning is: “If it blooms in the spring, prune the plant soon after flowering; if it blooms in the summer, prune in the spring.”
Therefore, now is a great time to prune summer blooming shrubs like crape myrtle, butterfly bush, clethra, some hydrangeas and other trees and shrubs not grown for spring blooms.
The most common reason people prune is to train a plant to a particular shape or size. A good example may be boxwoods grown as a hedge. Using hedge shears, it is easy to maintain a flat-top shape or even work shrubs into the shape of a ball.
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Although boxwoods will tolerate this treatment, this is not always the best pruning method. True, in a formal setting the clean, crisp lines of a boxwood are fitting, but have you every looked into the interior of these hedges? In most cases the actual leaves occupy only the outer two to three inches, leaving the interior bare.
You may also notice the dampness on the branches and lack of light within the canopy. This can lead to insect and disease development. Other pests, such as mosquitoes, will often use damp, dark areas to rest during the day.
Another option to shearing is to reach inside the plant and prune individual branches all the way back to the main stem. This breaks up the flat hedge surface and allows light and air to penetrate into the canopy of the shrub thus reducing favorable conditions for pests.
Other broadleaf shrubs with larger leaves grown as hedges (for example, holly and cherry laurel) should never be sheared since their leaves are too large and are often torn by the shears. These shredded leaves can serve as a site for disease infection.
Another reason to prune is to stimulate or increase flowering. By removing old, faded flowers during the year — a process called dead-heading — we can often encourage a plant to bloom a second or third time. This is good practice for plants like crape myrtle which, left unpruned, may only bloom once; but when dead-headed may bloom several times during the summer.
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Unfortunately with crape myrtles, many people take dead-heading to an extreme. Rather than removing the spent blooms or seedpods, they top or chop off the branches, usually near head height. This annual practice causes large, disfigured knuckles to form on the plant which are unattractive and can serve as a site for insect or disease damage.
This topping process has often been referred to as “crepe murder.”
The misconception is that the plant will produce multiple stems which are needed to have blooms, but all that really is needed is some light dead-heading.
Other pruning cuts should be made to dead or damaged limbs which reduce the health and vigor of the plant. Rubbing or crowded branches and suckers growing from the base of a plant should be removed to help eliminate problems before they start.
Be sure to use the right tools when pruning. Hand pruners work best on branches less than 1/2 an inch in diameter. Loppers are used for limbs from 1/2 to 1-1/2 inches in diameter.
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Both pruners and loppers should have scissor or by-pass blades rather than an anvil blade since the anvil-style will often crush stems and slow down healing. Pruning saws should be used to remove limbs larger than 1-1/2 inch in diameter.
You can do 90% of the pruning cuts on the trees and shrubs in your landscape with these three tools. But, it’s sometimes nice to have a little longer reach. In those situations, pole pruners or pole saws may be handy.
P. Andrew Rideout is the University of Kentucky Extension Agent for Horticulture at the Henderson County Extension Office. You can reach him by email at email@example.com