Time to Prune Your Deciduous Shrubs? It Depends!

By Master Gardener Sue White for the Black Hills Pioneer Master Gardener Column

Why Prune?  Most deciduous flowering shrubs need frequent pruning to look and perform their best.  This doesn’t necessarily mean every year.  Tour your yard, assess your shrubs.  Over-grown? Too full? Too tall?  Grab those bypass loppers and pruners.  Make sure they are clean and sharp.

But wait!  Is it the right time?  How do we know?

Flowering shrubs can generally be separated into two groups: summer flowering and spring flowering. Summer flowering shrubs, i.e., Hydrangea, Potentilla, Smoke Bush, Snowberry, Cotoneaster, most Spiraea, bloom on new wood, and can be shaped or pruned in March or early April. 

Spring flowering shrubs, i.e., Lilac, Forsythia, Chokeberry, Viburnum, Weigela, bloom on old wood and should not be pruned until after they have bloomed.  If they are pruned in the fall or winter, they will not bloom.

How much to prune? 

Yet again, it depends on what you want to do.  If your plant is not overgrown, consider renewal pruning which involves removing about a third of the oldest canes every year over three to five years.  If your plant is old and overgrown, you may want to rejuvenate it by cutting all the canes within 2-3 inches of the ground.  Many small shrubs may be cut back every year and will grow back and bloom.  However, cutting your mature lilac back to 3 inches may cost you blooms for several years. Remember: The season to prune depends on when your shrub blooms! 

How to prune? 

Shrubs produce canes, multiple shoots coming up from the ground.  Use heading cuts which are clean straight cuts made within 2 to 3 inches from the ground with loppers or sturdy bypass pruners.  This will encourage new shoots to emerge.  Shrubs that produce multiple canes should be pruned yearly or at least every few years.  Shrubs with only a few canes, such as burning bush should be thinned out occasionally rather than using heading cuts as described above.

Prune your Deciduous Trees?  It Depends!

You should only prune to help the tree!  And remember, if your feet must leave the ground to prune, find a certified arborist! 

Reasons for pruning trees: 1) to remove dead, diseased, or dying branches, 2) to remove low, crossing, or hazardous branches, 3) to train trees and control size, 4) to remove broken branches, 5) to protect people and property.

When to prune? 

It depends!  Pruning should begin at planting time.  Then only diseased, dead, or broken branches should be removed. Young trees will need all their leaves the first year.  Following the first-year, pruning done on young deciduous trees should be well thought out.  Remove crossing or rubbing branches.  Remove branches that are growing at an angle of thirty degrees or less relative to the trunk which are weakly joined and likely to break off in storms.  Trees should have one main leader, and limbs should be spaced about 6 to 18 inches apart.  Branches that are growing closer to the ground than you would like should be left in place until they reach about an inch in diameter.  Leaving these branches in place when they are smaller will benefit root development and a sturdier trunk. 

Remove dead or dangerous or diseased limbs as soon as possible any time of year.  Live branch pruning can be done as the trees are just breaking dormancy, but removal of small diameter branches less than 2 inches can be performed during the growing season.  Summer can be a good time to prune as the wounds will heal faster than when the tree is totally dormant.  Exceptions are elms that need dormant pruning and oaks not during April to June, due to incidence of diseases.  Often maples, walnuts, and birches, will exude sap “bleed” after pruning.  This causes little harm.  If you wish to avoid the sap flow, prune these trees in August.

Ready to cut?

Tools:  In addition to the bypass loppers and pruners mentioned above, a pruning saw with fine teeth that works on the pull is easier to use when reaching up.  Lysol and a clean cloth is necessary when removing diseased branches.  You must disinfect tools after every cut to avoid contamination.

Cut back branches to their point of origin, the collar, at the trunk or a lower branch; don't leave stubs.  Find the collar; the bulge that forms at the base of the branch where it intersects with the trunk.  Start your cut just outside the branch ridge, angling down to slightly outside the branch collar below.  This type of cut helps the wound heal.

Do not paint pruning cuts. Sealing cuts and wounds on trees does not speed healing and can promote decay.

More information: Free Tree Care Workshop Tuesday April 24, 2018 6:00 – 8:00pm.  Spearfish City Council Chambers. Direct questions to:  Northernhillsmastergardeners@yahoo.com