8 More Pruning Questions Answered

by Jan Cashman

My husband Jerry’s father used to say the time to prune is when your pruners are sharp.  That old nurseryman’s adage holds true for minor pruning, but now, in late winter when fruit and shade trees are dormant, is the best time to prune.  (However, do not prune maple and birch trees in late winter or spring because their sap will “bleed” through the pruning wound.  Wait until late summer.)  Here are some frequently asked questions about pruning:

Do All Trees And Plants Need Pruning?

No, not all trees need pruning.  Dead, damaged, old or diseased wood should be pruned out.  Pruning can be used to control the size or shape of a plant, but it makes more sense to select plants that will not outgrow their space.

Can Pruning Improve Fruiting?

Yes, thinning the branches on a fruit tree allows for consistent, larger fruit.  Pruning can open the center of the tree to allow sunlight to enter so the fruit develops and ripens.  Old wood on a fruit tree should be removed so young, vigorous, fruit-bearing branches develop.  Remove suckers that come up from the base of the tree and water sprouts (too vigorous vertical shoots that emerge from a horizontal branch).

Should I Remove Double Leaders In My Tree? 

Yes, leaving a single leader on young trees is preferable.  Narrow-angled crotches are weak and apt to split where wide-angled branches are stronger and resistant to breakage.

How Much Of A Tree Do I Dare To Prune At One Time?

Remove no more than 25 to 30 percent of a tree’s branches when pruning.

Is There A Correct Way To Make Pruning Cuts?

Yes, recent research has shown the healing advantage of pruning branches at the growth collar (a swelling of the union of the branch and the trunk).  Do not leave a stub where decay, insects and disease can enter.  When shortening shoots, cut just above a growth bud facing outward from the tree or shrub so the new growth does not cross and rub other branches.                                                                                                                                         

To avoid tearing the bark of a large branch, remove the branch with three cuts.  Start out from the crotch at least 6 inches and make an undercut about halfway through the branch.  Your second cut should fall the branch free of the trunk.  The third cut removes the remaining stub with no injury to the trunk.

Why Doesn’t My Lilac Shrub Flower?

Wait to prune until after your lilacs bloom so you don’t cut off the flower buds.  Use renewal pruning: remove the oldest branches to allow new young growth to form.  An old overgrown lilac can be cut off close to the ground and allowed to start over, but then may not bloom for a few years.  What holds true for lilacs does not hold true for all flowering shrubs.  Flower buds on shrubs such as roses and potentillas are formed on new growth, so pruning will not hurt their flowering.

When Should Evergreens Be Pruned?

It is best to prune most conifers in June when new growth has emerged.   Mugho pines can be kept dense by clipping off part of the new growth candles in June. Upright junipers and arborvitaes should be “given a haircut” every other year or so to keep them dense. Be careful when pruning evergreens not to cut them back too far into old wood.  Upright spruce, pines, and firs look most natural with little or no pruning.

What Is The Best Way To Prune Spreading Junipers That Have Become Overgrown?

Reach down into the interior of the juniper and cut back major branches which are about as long as your arm.  This allows light to penetrate to the interior so new growth can start there and create a natural, informal appearance.   After about 20 years, most spreading junipers are past their prime and the best solution might be to replace them.

Should I Use Tree Paint On Wounds After Pruning?

The latest thinking is that tree wound dressings are not needed on pruning cuts.  A callus will close the wound naturally with exposure to air.

March or early April on a day when the temperature is above freezing is the best time to prune most trees and shrubs.   Sharpen your pruners and head outside to improve your plantings!

See also…

This is a follow-up article to our “10 Often Asked Questions about Pruning”, which may answer more of your questions.