The grounds burst with color the past few weeks as flowering rhododendrons took the spotlight. This particular specimen towered near one of our trails and greeted passerby’s with numerous, large purple blossoms that covered the entire shrub.
But now, flowers have faded and its time to put forth a little extra maintenance to keep these and other spring flowering shrubs looking their best for years to come.
Here at the inn, there are many rhododendrons of various sizes, ages, and locations. Many had dead/broken branches, lanky stems/weak growth, and needed some shaping up. Most importantly, I took time to remove spent flowers, called trusses, as these take energy from the plant that can otherwise be used toward vegetative growth. To remove, use pruning shears to snip the truss at its base, about ½ inch above the emerging flush of new growth. Charles W. G. Smith authors an excellent article on 3 Ways to Prune Rhododendrons: maintenance pruning, pruning for shape, and rejuvenation pruning.
- Maintenance pruning simply removes old flowers as mentioned above, and dead or diseased wood. This is best performed immediately after flowering.
- Pruning for shape removes branches to increase branch density or control size/width.
- To prune for shape, follow the branch from the end to above the whorl of leaves you want to keep. Make a cut about a ½ inch above that whorl. This pruning is best performed in late winter while the plant is dormant, though this will sacrifice some flower buds. If most leaves are at the ends of branches, cut back to four or five inches above a fork of branches.
- Rejuvenation pruning is a drastic pruning technique for leggy/old shrubs that stimulates new growth from the base. There are different methods to choose. Rejuvenation pruning is best performed in late winter during dormancy.
Rhododendrons have three or more main branches. These primary branches can be cut back at different heights to produce a staggered look. Look for swollen, pink buds along the branches and cut about ½ to ¾ of an inch above.
Another option is cutting the entire plant back to about 6 inches. You may want to try one branch and watch what happens before cutting the plant back in entirety.
With the variety of rhodos around the inn, I was able to experiment with all three types of pruning. I look forward to monitoring the effects of my pruning cuts and sharing my results with you.
Keep in mind, spring/early summer is the time to prune other spring flowering shrubs immediately after their flowers fade, next year’s flower buds will develop on the new stems. This includes shrubs such as lilac, forsythia, viburnum, etc.