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Monday - July 25, 2011

From: Mohnton, PA
Region: Mid-Atlantic
Topic: Pruning
Title: Cutting back perennials in PA
Answered by: Anne Bossart

QUESTION:

Can you pinch back echinacea in the spring to produce a shorter plant? I have some that get too tall and fall over.

ANSWER:

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)

Phlox paniculata (Fall phlox)

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.