By Carol Anderson, Master Gardener in Training

Spring is upon us and most of us are venturing out into the garden to undertake some much needed clean up, anticipating the beautiful days and growing season ahead. However, do you find yourself looking at your shrubs and wondering whether to prune or not, and if so, when, and how? If this describes you, then this blog might be helpful as you consider your spring work ahead. Although we know that pruning supports the growth of healthy and robust shrubs, it is one of the most inconsistent and often poorly executed garden techniques. Pruning is not only essential to maintaining plant health, but also an essential part of woody plant maintenance used to:

ü  improve the quality of your plant/shrub (e.g. flowers or yield),

ü  “train” plants (shape and structure),

ü  remove dead of broken branches,

ü  control their size and shape, and

ü  create an esthetically appealing specimen in your garden. 

Perhaps the reason that pruning is avoided by many gardeners is because proper pruning takes careful planning and execution; knowing your plants growth habit (mounding, cane or tree-like) and life cycle will determine pruning time and technique to be used. The following tips will hopefully turn this daunting task into something more enjoyable.

1. Develop a pruning plan for your garden – a plan that outlines each plant’s pruning requirements (including timing). Create a table that identifies, at a minimum, what species of shrub you have, its location in the garden and when to prune. In addition, you may wish to add details and notes about any observations you have made and when it was last pruned. Keep this plan as a reference tool going forward.

2. Determine your objective for pruning – are you cleaning up broken or diseased branches? Is the shrub too big? Is the shrub dying in the middle and too dense? Or is the shrub very old and has lost much of its’ vigour?

3. Determine how much to prune – rule of thumb: don’t remove more than 1/3 of a shrub in any one season (Exception: if you are undertaking gradual or extensive rejuvenation pruning – see below)

4. Understand the proper tools and technique to use – general rule of thumb is that secateurs can be used for branches up to ¾” and lopping shears up to 2” branches – anything beyond that may require a specialized saw. Cuts should be clean and taken back to the next lateral branch, node or close to the ground (described below), but never randomly in the middle of a branch.

5. Determine when to prune – the following table provides an overview of pruning objectives, techniques, and timing.

Special Note: most evergreen shrubs do not need pruning, except sanitation pruning as required. The proper selection of the shrub and then allowing them to grow to their natural form is always recommended, unless you are training them to a specific form. Evergreen shrubs require special consideration as they cannot withstand the pruning described here for deciduous shrubs.  

Pruning Objective	Purpose	Technique	Timing
Sanitation Pruning	Used to remove dead, dying or diseased branches. Note: broken stems can lead to disease and insect infestations	Cut below area of damage (into healthy wood) just above an outward facing branch node	Throughout the growing season (inspection of your shrubs should be done regularly)
Thinning	Used to improve air flow and light penetration and prevent branches in the middle or bottom of the shrub from dying; thinning stimulates growth throughout the shrub	Remove branches to their point of origin (next lateral branch). Note: for shrubs with cane type growth, remove the oldest growth cane close to the ground	*Regardless of the objective and method, it is important to know whether the shrub blooms on “new” growth (this year’s branches) or “old growth” (branches formed the previous year). For example, a Common Lilac blooms on last year’s growth – pruning right after blooms dies off will ensure sufficient time for new growth to become established  prior to dormancy and exposure to harsh cold temperatures.
Reducing Size	Used to reduce the overall size of the shrub. Note: it is recommended that when choosing a garden shrub, the mature size should be considered given the space	“Head-back” to the next lateral branch that is at least 1/3 the size of the one being removed
Stimulating Growth	Used to improve overall yield of flowers or enhanced foliage growth (bushiness)	Head back to an outward facing bud (new growth will be stimulated at the bud closest to the cut and in the direction the bud is facing)
Rejuvenation Pruning	Older shrubs have large portions of unproductive wood; these are removed to stimulate new growth	Gradual: requires ~ 3 years of gradual removal of old and new shoots Extensive: removal to 6-10” from ground with gradual removal of some of the new growth

*In general, spring blooming shrubs most often bloom from buds formed on last years’ “old growth”, such as the Common Lilac. In contrast, most summer blooming shrubs will flower on “new growth” requiring a late winter/early spring prune to stimulate new growth for flowering in the same year, such as most Hydrangeas. Pruning your shrubs (and trees…although not covered in this blog), should become an essential technique to managing your home garden – and it will pay off in spades (😊).

Be clear on your objective before starting and take notes that will guide you in subsequent years. Do not be fearful of doing some rejuvenation for those shrubs that are just not what they used to be; but it is recommended that you do some homework on this technique before embarking on anything extensive. So get out those secateurs, clean them thoroughly and start pruning – your shrubs will thank you for it!