Fall Pruning...Rules of the Road

In my observations, pruning continues to be one of the most intimidating garden routines for most homeowners.  Knowing the how’s and when’s of pruning isn’t as difficult or complicated as it seems once you have just a little bit of inside knowledge going into the process.  For now, let’s look at fall pruning (and plant care) so we can gain confidence in this elemental gardening task.

The first thing to understand is that pruning encourages new growth.  This can be a good thing, or a bad thing, depending on your situation.  In the fall, it is very important that we allow ample time for the new growth on pruned plants to “harden up” before freezing winter temperatures set in.  For this reason, we generally suspend most of our pruning activities on trees and shrubs from mid-September through Thanksgiving.  By December, our trees/shrubs will be completely dormant and will no longer be able to push new growth. 

A common fall pruning mistake made is the trimming off of next year’s flower buds on spring blooming trees/shrubs.  Plants like Forsythia, Viburnum, Dogwood, Azaleas, Lilacs and Magnolias develop their flower buds during the summer months and trimming them in the fall would mean you would have no flowers for next year.  Wait to prune these plants until right after they finish blooming next spring.

Boxwood is generally very hardy in our area however it can be damaged during very severe winter weather.  While this does not occur often, it is best to plan (and prune) for the worst-case scenario.  Boxwood that is sheared very tightly in the fall is much more likely to be damaged than plants that have not been cut back late in the season.   For this reason, do not prune any Boxwood between September 1^st and Thanksgiving.

This does not mean there isn’t any pruning done during the fall season.  Most all your perennial plants can be cut down in fall if desired.  Those of us who desire a tidy garden will appreciate getting all the dormant foliage off the perennials after they freeze down in November.  Another school of thought is that leaving the foliage in the garden helps protect the plants over the winter.  There are a few plants we think of as perennials that should not be pruned back in the fall.  These sub-shrubs retain green growth through their stems in winter that helps them store vital energy to help them sustain cold temperatures.  Examples of sub-shrub perennials that should not be pruned in fall include Butterfly Bush, Russian Sage, Thyme, Lavender, Roses and Caryopteris. 

Perhaps the most helpful information a homeowner may benefit from gathering is a list of the plants that you have in your landscape and the pruning/care for those specific plants.  It is much more difficult to learn how to prune all plants than it is to just learn about your own.  Having a qualified professional visit your home and prepare a list of your plants and the accompanying care they need can be very valuable for those who desire to perform their own plant care/pruning. 

I wish I could say that having pruning work done for you could eliminate all this confusion however that couldn’t be further from the truth.  The fact is that many landscape professionals lack the knowledge required to provide proper pruning.  Utilizing some of the information I have provided you here should help you ask some specific questions to help you determine if the person you are speaking with knows how to prune.  

While proper pruning cannot make up for poor design decisions (10’ plant in front of a 4’ window), pruning does help your plants perform to their fullest and greatly extends the potential lifespan of your landscape investment.  Even if you choose to do your own pruning it is a worth-while investment to have a professional look at your landscape every 3-4 years just to help you maintain your landscape plants and keep an eye out for potential problems.

Now go have fun in the dirt!