Shrub Pruning in Late Summer

By Sally McNamara  and Janet Poore, Master Gardeners

Please note that this article discusses late summer pruning.  Once Fall arrives, pruning should cease, except for storm damage of course.  Pruning in fall encourages growth which will not harden off properly before temperatures fall, exposing that growth and the connected branch to injury or death.

Late summer pruning is done for two reasons: 1) damage or disease removal and 2) shrub renovation.  Those shrubs that bloom in the spring should be pruned right AFTER blooming so as to NOT cut off next year’s blooms.  Lilacs, forsythia, mock orange, azaleas & rhododendron are examples of shrubs to be pruned after blooming in the spring.  If renovation is more desirable than next year’s blooms, they can be pruned over the summer or even in the prime pre-spring pruning window.  Renovation is often best undertaken when the actual shape of the leaf-covered plant is visible. 

Plant material damaged by storms, hail, pets, sports in the yard, etc. should always be removed for safety reasons and to limit input points on the plant for disease or insects.  This is true in every season.  Unless there is disease in the pruning, this material can be discarded with regular yard waste.

Plants damaged by disease should be pruned to minimize the spread of the disease.  Use the U of M Extension site to identify the problem.  After pruning diseased material, sterilize tools and gloves used to halt the spread of the disease.  Hand sanitizer, anti-bacterial wipes, Lysol, Pine-Sol and Listerine are all good disinfectants.   Diseased material should NOT be put in the regular yard waste but should be placed in a plastic bag, sealed and set in the sun for several days before discarding in the regular trash.

Late summer is a less busy time in the garden and is a good time to assess how your shrubs are working in your landscape.  If some have become a little “aggressive” or even (horrors!) “shabby,” now is a good time to rein them in.  Most deciduous shrubs can be pruned at this time to improve their shape and size.  Note that this is NOT true of evergreens except Yews!  Evergreens should only be pruned in the spring when their candles are present.  The pruning goal is to reduce the plant to the size desired and thin out from the inside, removing inner branches to increase airflow through the plant which encourages healthy growth.  Remove the oldest, woody stems right down to the base.

One caveat – hedges are often prime nesting places for birds so check for “residents” before taking on that hedge.  Wait until the fledglings have taken wing. 

Some plants which react well to late summer pruning:

Notice that hydrangea is absent from the list.  Pruning hydrangea depends on the type of plant and varies widely.  Also, most hydrangeas are in best bloom in late summer.  Julie Weisenhorn has a good description of hydrangea pruning on this U of M Extension website. Remember that there are right and wrong ways to prune bushes. For advice about proper methods of pruning, look back at our article from the March 2022 Garden Buzz – March is a Great Time to Prune Many Trees and Shrubs – currently found on the Master Gardeners in Dakota County website.

Some shrubs can be pruned later in the summer but not all of them, so get to know when it is okay to prune the shrubs in your yard.