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Update on Blue Mist Spirea Pruning

Back in May, I wrote a post about three common methods used to prune blue mist spirea in spring. Let’s take a look at some plants that were cut using each of the three methods.

Be sure to check out this video about how to cut back or prune blue mist spirea in spring

Not cut back at all

Blue mist spirea unpruned

When a blue mist spirea shrub is left unpruned in spring, the old, dead flower stalks obscure the new growth.

Here’s what a blue mist spirea shrub looks like if you don’t cut it at all in the early spring. Notice the new leaves have begun to grow on the bottom two-thirds of the plant. However, last year’s dead flower spikes are still present. When the shrub blooms in July, the brown flower spikes will obscure this year’s flowers, making the shrub look neglected, sick, or simply odd.

If you have a Caryopteris plant that hasn’t been cut back yet, it’s not too late to take action. Use the second method (cut to new growth) in my previous post. Cut the dead portions off the plant and prune for symmetry before it flowers in July. You’re still likely to be rewarded with a pleasing set of blossoms.

Cut back partway

Blue mist spirea branches pruned partway

When old blue mist spirea branches are pruned partway back, the cut stubs become an eyesore.

You can see from the picture why this is my least favorite method. The new growth emerges from the older stems, but the shrub doesn’t look that great with half of the old, thick stems left behind. When branches are cut at a certain length without a good horticultural reason for the cut, the result is irregular growth. In fact, the cut stubs become an eyesore.

It’s true that the new growth will eventually cover the cut stubs, but there are a few months in spring where the old stems are pretty noticeable. Plus, when the plants lose their leaves in fall, the less-than-attractive branches will be visible once again.

Cut back to new growth

Blue mist spirea pruned to new growth

Blue mist spirea shrubs cut to new growth, then shaped for symmetry look healthy and full

This method is a pretty good option. On most of the blue mist spireas I’ve seen recently, the gardeners were successful at removing all of last year’s dead growth. They also shaped them for symmetry. These two accomplishments result in a nicely shaped shrub with green growth and attractive flowers when bloom time arrives. The take away message is that if your shrub has a nice branching pattern, pruning to new growth is an effective method to use.

Cut back to ground level

Back in May, I mentioned that this was my favorite method for blue mist spireas under 7,000 feet in elevation. I still believe this is true, but some of the plants I cut to ground level have been slow to recover. They’re smaller than normal at this time of year.

Blue ,mist spirea after cut to ground level

After blue mist spirea is cut to the ground in the spring, the stems grow back fresh, green, and uniform.

Because we had a cold spring, they’ve grown more slowly. So although the old stems are removed and the new growth is symmetrical and fresh, they’re small.

Are they going to bloom on time? Good question. I’ll keep an eye on them and see how the bloom time compares with shrubs that were pruned to the new growth. Stay tuned for the results next month!

Happy Father’s Day to all the dads out there. Hope you get a chance to relax today. 🙂

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2 Responses to Update on Blue Mist Spirea Pruning

  1. Tami May 16, 2017 at 10:35 am #

    Hi Catherine – Thank you for all of the helpful tips on blue mist spirea. I realize I’m commenting on an older article, so I hope you will see see this. We had followed your advice on trimming our new blue mist spirea (planted July last year). But, then we had the ice/snowstorm a couple of weeks a go and our blue mist do not look happy. I’m wondering if we should trim them back down again or just take our chances? With a possible snow/ice event coming this week, is it best to cover shrubs which are just emerging? Thanks so much!

    • Catherine May 21, 2017 at 6:09 pm #

      Hi Tami, So sorry for not responding sooner. I hope your blue mist spireas have fared okay with all this wacky weather. I was out looking at trees and shrubs this weekend. Although a lot of them have frost-damaged leaves from the last cold spell, they’re starting to outgrow it. They will continue to have some black or brown crispy leaves which don’t look great, but many trees and shrubs are starting to grow new leaves that will eventually cover they damaged ones. I wouldn’t do any more pruning at this point. As the shrubs start to grow new leaves over the next few weeks, you can run your hands over the damaged leaves towards the bottom/inner part of the shrub so the crispy parts to break up and fall off the branches. It will look bad for a few more weeks, but if your plants are healthy the new leaves will eventually cover up the frost damaged leaves. Hope that helps!

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