Many shrubs will look their best when allowed to grow to their natural form with just occasional pruning of dead, damaged or diseased wood. Avoid making cuts at a uniform edge creating a round ball or other unnatural shape or across the top of a shrub.
This is a common pruning technique because it is quick and easy.
Frequent, unnecessary shearing that is done incorrectly can cause shrubs to lose their natural shape, resulting in an unhealthy structure with dead sections and reduced flowering.
If you really want a tightly sheared look in your garden, choose a plant that is suited to this type of pruning such as boxwood.
1) Branch by Branch Shaping
One proper pruning technique is branch by branch shaping which involves cutting the longest and oldest branches back to the point of origin where the branch grew from its parent branch. This results in branches of varying lengths and a more natural looking shrub. It is an acceptable method for deciduous shrubs but does not significantly encourage new growth of wood on flowering shrubs for maximum bloom.
One of two methods to encourage shrub flowering is thinning. The objective is to cut one-third of the oldest wood to the ground each year which stimulates new, better flowering growth from the base of the shrub. This method is time-consuming and does not work well on twiggy, multi-stem shrubs like spirea. For overgrown shrubs, it is best to do rejuvenation pruning, followed by thinning.
The other method to encourage shrub flowering is rejuvenation. Rather than just cutting one-third of the oldest wood, the shrub is cut entirely to the ground or just above it in the early spring before new growth starts. The shrub regrows from the roots, giving a compact new plant with maximum bloom. This method is preferred for many flowering shrubs such as multi-stemmed, twiggy-type shrubs such as Spirea, Blue Mist Spirea, Potentilla, Red-twig Dogwood, Sumac, and Hydrangea. You can also use this method to rejuvenate Lilac, Privets, Barberry, Forsythia, Quince, Mockorange, Weigela, and many Viburnums. Rejuvenation should be followed by thinning new canes to several strong ones over the next several years with weak cane growth removed at the base. After three to five years, rejuvenation may be repeated again when the shrub begins to look woody.
When To Prune – To Be Continued
About Urban Gardens, Inc.:
Urban Gardens provides landscape design and consulting services to residential clients whose projects range from historic renovations to new subdivisions with a blank slate. Sarah Christian owns and operates Urban Gardens in the internationally recognized Stapleton Development in Denver, Colorado. She received her Masters degree in Landscape Architecture from the University of Colorado at Denver in 1995 and has worked in Colorado since that time. She is licensed by the state of Colorado and is a member of the American Society of Landscape Architects. You can visit her web page at www.urbangardensinc.com