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From: Mohnton, PA
Region: Mid-Atlantic
Topic: Pruning
Title: Cutting back perennials in PA
Answered by: Anne Bossart
Yes you can, but not this year.
There are a number of late-summer/fall blooming perennials that can be cut back by half in late spring/early summer. As a result, they will be shorter and sturdier (less likely to need staking or fall over). They will also be bushier and more floriferous.
I have had a similar problem in one of my perennial beds and tried it this year on:
Aconitum delphiniifolium (Larkspur-leaf monkshood)
Monarda didyma (Scarlet beebalm)
So far, so good ... the monarda is blooming on schedule at a shorter height than usual and the other two seem to be budding. I am in zone 5 and did it late in May ... you will want to do it a little earlier than that.
Besides these three and your Echinacea purpurea (Eastern purple coneflower), you can also give the same treatment to:
Eupatoriadelphus maculatus (Joe-pye weed)
Physostegia virginiana (Fall obedient plant)
Symphyotrichum oblongifolium (Aromatic aster)
and the tall sedum varieties.
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