Winter Pruning for Summer Blooming

Spring is around the corner and, if you’re feeling like we are, you’re beginning to get that itch to get back into your yard.  So what can you start in on while there’s still snow cover?  You may know that winter and early spring pruning can be beneficial to your landscape, but you also may find yourself hesitant to begin.  What exactly should you be pruning this time of year?  More importantly, what SHOULDN’T you be pruning?  And once you’ve determined what to trim, how do you go about it?  Read on for the when, why and how of winter pruning, plus our “rules of thumb” to bring the most benefit to your trimming efforts!

First off, establish why you are pruning.  Before you pick up those shears, consider these points and determine your final goal.

  • Pruning to remove dead or diseased portions of the plant:  Deadwood does nothing positive for your plants.  In fact, it does just the opposite by encouraging rot and providing brood space for the insects which feed on our landscapes.  Having leaves on the plant in question will obviously help determine which branches to remove, so this type of pruning is typically recommended once your plant has its foliage.
  • Prune to develop the plant’s structure:  The structure of a plant might be compared to our skeleton.  Strong trunks, branches and limbs provide stability and strength against wind, rain, snow, and ice.  Also, look to eliminate any future hazards by proactively removing weak branches, crossing branches or over-hanging limbs.
  • Prune for aesthetics:  This is your chance to determine a plant’s size and shape as it fits into your particular landscaping scheme.  The aesthetics of how you prune is up to you; but please remember each plant has its own natural shape in which it chooses to grow.  When pruning, considering the natural shape of your plants will aid in its overall health. 

Pruning for your plant’s structure or aesthetics often falls into the category of “renewal pruning”.  If your deciduous plants are invading your home’s space, or your flowering shrubs and hedges are becoming tall, leggy and thin, renewal pruning can bring your landscape back to life in a few easy steps.  And for most plants, it’s most beneficial to complete in the dormant months (like February), when the plants have no leaves.  Here are a few basic tips for optimal renewal pruning:

  • Begin by looking closely at the shrub to determine the oldest branches and stems that form the plant.  Simply put, the oldest stems will be the biggest.
  • Using the proper tool (shears for branches up to ½” diameter, loppers for branches up to 1” diameter, and a saw for branches 1”+ in diameter) remove the oldest branches by cutting them as close to the ground as possible.  Do not remove more than 1/3 of the plant’s entire growth.
  • Repeat this process for three seasons (removing 1/3 of the branches each season) until all the old growth has been removed.

How exactly does this help?  Each year the plant will strive to replace the branches you’ve removed.  New growth will be generated from the base filling in the bare spots.  The oldest stems are also usually the tallest, so this process naturally helps in controlling height as well.

In extreme situations you may opt to literally cut the entire plant right down to the ground.  This is useful for plants like an over-grown Sandcherry and those with numerous stems like Spirea and Potentilla.  This process is called “rejuvenation pruning“.  Rejuvenation pruning is not recommended for all plants, as some simply do not respond well to this method. Lilac would fit this category. 

Before you set out on your winter pruning tasks, keep in mind these general rules of thumb to help ensure an optimal outcome:

  • Try to limit pruning the first year or two of a plant’s life.  This keeps the maximum amount of foliage on the plant producing the maximum amount of nutrients as the plant works to adapt to its new home.
  • Summer blooming plants are best pruned when the plant is dormant.  This includes late fall and early spring.  Examples of summer bloomers would be potentilla, spirea and hydrangea.  REMEMBER that summer blooming plants set their buds in the spring.  Pruning once the growth has started each spring will remove the flowers buds for the summer ahead.
  • DO NOT trim early flowering shrubs now, such as Forsythia, Lilac, Mockorange, and white flowering Spirea because you will lose some of the flowers.  Spring blooming plants set their flower buds in late summer or fall.  Pruning after that will actually remove the flower buds.  Spring blooming plants are best pruned immediately after they flower, which will remove any spent blossoms and keep your shrub in shape for the summer ahead. 
  • DO NOT trim “bleeder trees” such as Maple, Elm, and Birch, because they will lose much of their sap in the spring.  Trees that bleed readily in the spring are best pruned during the late summer. This allows abundant time for pruning wounds to heal.