Pruning Trees and Shrubs

Thinning out raspberry canes.

 

When is the best time to prune?

The crossing branches of this burning bush are an entryway for disease since the rubbing leaves open wounds. These should be pruned out.

The crossing branches of this burning bush are an entryway for disease since the rubbing leaves open wounds. These should be pruned out.

Late winter and early spring are generally the best times to prune most trees and shrubs. There are some exceptions, such as broad leaf evergreens that bloom in early spring, and should be pruned after blooming.  Certain conifers need pruning when new growth is pushing out, but dormant pruning is often a recommended time for many plants. 

The terms "late winter" and "early spring" can be confusing. When is that exactly? It is the time when the seasons meet; when winter is exiting and spring is arriving. This time frame is defined as dormant pruning.

Dormant pruning just before growth begins leaves a wound exposed for the minimum amount of time before healing begins. (Lee Reich, The Pruning Book).  

Prune before the buds start swelling, but not so early in winter that the plant could suffer winter injury. Winter injury is a term that defines several types of plant damage caused by environmental conditions, frost injury being one of them. In Western North Carolina, that means you can begin pruning now and continue through the first few weeks of March, since Spring arrives March 20th.

Why do we prune?

If you're going to prune, have a clear objective in mind as to why and what for. Also, understand your plant and its response to the pruning. 

Thinning out the interior of this forsythia will allow light and air circulation into the shrub. Light inhibits the growth of certain diseases and air helps keep leaves and shoots dry.

Thinning out the interior of this forsythia will allow light and air circulation into the shrub. Light inhibits the growth of certain diseases and air helps keep leaves and shoots dry.

The primary reasons for pruning are:

  • Health
  • Size
  • Bounty
  • Beauty

Every plant has different pruning needs and a good reference book is helpful when determining how and when to prune your hydrangeas, crepe myrtles, broad leaf evergreens and conifers (for conifers, pretty much never), and so forth. But no gardener should ever wait to prune out dead, diseased and damaged wood. That's one chore you can do in any season. It helps prevent disease and pests, as these open wounds serve as the perfect portal for both.

Size is the most common reason people prune, as foundation shrubs overtake the front of the house and trees outgrow lot sizes. The hope is that consumers buy a plant that fits the space allotted it, but that isn't always the case, and gardeners can be faced with tackling overwhelming shrubs. 

How do we prune? 

This holly has overgrown the front of the house. In this case, the homeowners prefer it for privacy, but neither the house nor the shrub benefit in this setting.

This holly has overgrown the front of the house. In this case, the homeowners prefer it for privacy, but neither the house nor the shrub benefit in this setting.

  • Cut out all diseased, damaged and dead wood. 
  • Thin out crowded and dense limbs.
  • Remove watersprouts from limbs on trees.
  • Remove all crossing or rubbing branches.
  • Remove weak wood.
  • Remove pencil thin growth.
  • Cut back at least 6" to healthy wood on any dead wood.
  • Remove suckers.

Types of Pruning:

  • Heading
  • Thinning
  • Pinching
  • Shearing
  • Rejuvenation

The plant and its needs will determine the type of pruning to be done. Most deciduous shrubs are going to benefit from thinning or heading, or both. Removing old growth at the base of the shrub, and new pencil-thin stems (thinning), will give room for air circulation and light. Heading back branches forces energy reserves into shoot and bud formation. The general rule of thumb is never removing more than 1/3 of the plant at one time. Most homeowners are too nervous to cut and, therefore, don't cut enough, especially with fruit trees and berry bushes where cuts result in a bountiful harvest by redirecting energy into greater fruit production and less plant growth.

 

Thinning shrubs allows light and air to better penetrate the shrub. Removing old wood helps keep a shrub young and vibrant.

Rejuvenation pruning is often done on old shrubs, but also on deciduous shrubs that look best with the current year's growth (red twig dogwood).

Heading back shrubs promotes branching and increases flower/fruit production.

Heading back shrubs promotes branching and increases flower/fruit production.

Shearing hedges so that all parts of the plant receive light creates healthier hedges.

Pruning can improve the health, vigor, and lifespan of your plants. If you have questions regarding specific trees or shrubs, your local extension service is a good place to start. The store also has resources and staff that can answer your questions.

Written by Cinthia Milner, Garden Coach, OSA, and blog writer.

BB Barns serves Asheville, all of Western North Carolina, upstate South Carolina, and Tennessee.