I have been writing about the importance and how-to’s of pruning and today, the topic is one of my favorites – rejuvenation pruning. This is an easy technique and one that brings new life into old straggly shrubs.
Woody deciduous shrubs such as weigela, forsythia, spiraea, and others tend to get overgrown if not pruned periodically throughout their life. When this occurs, rejuvenation pruning can be used to get them back in shape.
Before I get into how you complete this technique, let me first suggest that you put the right plant in the right place. Don’t put a 15-20 foot forsythia in a four-by-four foot spot near the house. You must prune this every year to keep it in its confines.
The great news is that there are numerous varieties of shrubs today that are smaller, more compact, and much more suited to these sites. And for the most part, they don’t need regular pruning.
For example, I have a lilac cultivar that is planted near my house and the maximum height is four feet tall by three feet wide. I have not pruned them except for the removal of any dead wood or errant branches.
This is my idea of low maintenance – shrubs that don’t require yearly pruning to keep them in bounds.
To rejuvenate a woody deciduous shrub, you simply cut all the branches back to about three to four inches above the ground. This can be accomplished between now and the time that new growth starts to show this spring.
Because woody deciduous shrubs store their food source in the roots over the winter, once new growth begins, all the food from the roots is put into developing new branches. This rejuvenated plant looks much better and will be easier to keep pruned.
Notice I say woody deciduous and not evergreen shrubs. Evergreens store food in their leaves. If you cut evergreen shrubs back to the ground, it will take a long time for them to recover, if at all.
Cutting off their stored food (foliage) and not having leaves to continue photosynthesis puts an evergreen plant under a lot of stress.
That said, you can cut them back and prune them at this time, but the further you cut them back, the longer it will take to recover.
A good rule of thumb for evergreen shrubs is to cut them back to pencil-sized stems if you are going to rejuvenate them.
There are some large shrubs such as lilacs and viburnums that can be rejuvenated by removing the older branches and allowing the younger branches to take over. This process can be completed over a three-year period.
Remove one-third of the older branches each year. The plant will send up new growth to fill in and look a lot better. Again, doing this before the foliage comes out this spring is the best time to do it.
Next week, the final article on pruning evergreen trees and the difference in timing of pruning spruces and pines.
Pamela Corle-Bennett is the state master gardener volunteer coordinator and horticulture educator for Ohio State University Extension. Contact her by email at email@example.com.
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