Is Caryopteris a perennial or a shrub? It doesn’t seen to die back all the way to the ground, but seems like it does have some deadwood on it each spring. I never know how and when to prune it.
Caryopteris, commonly known as bluebeard spirea or blue-mist spirea, is really a woody shrub in more southern areas of the country. Here in Michigan we should consider it a woody perennial since the amount of spring dieback will vary with the severity of the previous winter. Many other shrubs commonly grown in our area can be treated in a similar manner. These include: butterfly bush (Buddleia), beautyberry (Callicarpa), bushclover (Lespedeza) and Hypericum.
Spring pruning can be approached in one of three ways:
- Prune all of the stems down to 6 to 8 inches in early to mid-April. This keeps your shrubs approximately the same size each year since they begin their growth from the same starting point.
- Wait until May when buds begin to swell and growth emerges. Any wood that remains inactive can be pruned off at this time. Scratching the bark with your thumbnail will also reveal where green living wood merges into brown tissues where dieback has occurred.
- An intermediate approach (especially useful after mild winters) is to prune the plant back in April by about one-third to help the shape and overall neatness. Wait until growth emerges later in May, then prune off any winter dieback that remains. Methods 2 and 3 will allow the shrub to gain additional size each year as long as winter conditions allow.