This arrowwood viburnum (Viburnum dentatum) is part of a hedge that had gone unpruned for more than five years. Last summer, the branches splayed out onto the lawn. Though it bloomed beautifully, it was an unruly green mass. To keep the shrub upright, we used rope, which was partially effective. But what it really needed was restoration pruning.
Pruning is one of those things that intimidates new gardeners — even some of us who’ve been doing it for a long time. True, you can do a lot of damage if you go about it in the wrong way. And if you want to take on complex pruning jobs — such as restoring fruit trees or shaping hedges — it makes sense to get a good book on the subject. I recommend The Pruning Book by Lee Reich. But, with a few simple guidelines, even a beginner can prune ornamental shrubs successfully. In general, your goal with any ornamental shrub is to:
- Remove dead or damaged wood
- Open up the shrub for better air movement
- Reduce height, if desired
Start in late winter, before the leaves come out. It’s much easier to see what you’re working with. Plus, you get to be in the garden — at last!
Make sure you have a set of quality tools. For most jobs, you can get by with a set of hand-held pruners and a pruning saw for bigger branches. For big jobs, it’s handy to have a loppers to take care of branches that are too thick for the hand pruners. Don’t skimp on quality. Good tools are more expensive, but they make the job easier and more efficient.
It’s important to identify each shrub before you prune. If you don’t know what it is, find a neighbor that can help you, or contact a Master Gardener via your county cooperative extension service.
Why? Some shrubs should not be pruned in spring. In general, spring bloomers, such as magnolias and lilacs, should be pruned after they bloom. There’s an old saying about lilacs: prune after they bloom but before the Fourth of July. Any later and you risk cutting off the next season’s blooms. For these early-flowering shrubs, just look for dead or damaged wood and remove it.
Once you’ve identified your shrub as a candidate for late-winter pruning, look for dead or damaged wood. Remove it, using hand pruners or the pruning saw for larger branches.
If you want to keep the shrub compact, consider removing some of the older, thicker branches and leaving the younger ones. With many shrubs, you can remove the entire branch, right to the ground. Another reason to remove some of the old wood: It relieves congestion and opens up the shrub. Better airflow means less chance for diseases, such as powdery mildew.
To renew the viburnum hedge, I used a pruning saw to take out about a third of the older branches — right at ground level. Then, I reduced the height by 1 to 2 feet. The “tough-love” pruning looks a little harsh, but the effort will pay off.
After you’ve thinned the shrub, stand back and take out branches that don’t “fit” the structure of the shrub. This is subjective, so do what you think is right. In some cases, it’s just a matter of trimming a gangly branch or two. As you work, keep looking for dead or damaged wood that you might have missed.
If your shrub puts out a lot of suckers — fast-growing branches that appear at the base of the shrub — you might want to remove some of them, especially if the plant is growing vigorously.
That’s it. During the year, pay attention to how your pruned shrubs grow and make notes for next year. Again, it’s pretty important to identify your shrub before you start making cuts. For instance, hydrangeas benefit from special pruning techniques. The popular blue varieties are best pruned right after blooming. However, white Annabelles and PeeGees can be pruned hard in spring.