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Cutting Back Perennials in Fall

To cut back or not to cut back? That is a question gardeners ask when temperatures cool, leaves turn color, and days grow shorter.

Most perennials don’t care if they are cut back in fall or left standing in the garden until spring. Gardeners, on the other hand, may have strong opinions on the subject. Some tidy gardeners prefer the look of a blank slate when snow falls on their landscapes. Others are dispassionate – cut or don’t cut. The remaining camp of green-thumbers is vehemently opposed to cutting perennials back in fall, preferring to leave it all standing until spring.

I am pragmatic in my approach to fall clean-up. I would never have enough time to cut everything back in fall OR spring, so I cut about half of my perennials back in each season. I do, however, follow these general guidelines to decide when to put my pruners into action and when to put them away.

Rudbeckia ‘Goldsturm’ offers nutritious seeds to hungry birds.

WAIT to cut back perennials that feed the birds.
Some perennials offer nourishing seed heads for birds. Black-eyed Susan (Rudbeckia), coneflowers (Echinacea), goldenrod (Solidago), and perennial sunflowers (Heliopsis) are just a few.

Native bees and other pollinators use parts of the cup plant to build their nests in the soil beneath them.

WAIT to cut back perennials that provide shelter for beneficial insects.
Native plants, like cup plant (Silphium perfoliatum), spiderwort (Tradescantia ohiensis) and bee balm (Monarda fistulosa), offer shelter to beneficial insects that overwinter in or near them.

Agastache ‘Blue Fortune’ needs a little extra protection in harsh winters.

WAIT to cut back perennials that need extra protection to make it through the winter.
The foliage left standing over some marginally-hardy perennials or those prone to frost heaving gives them a little extra protection. The stems catch wind-blown leaves and snow, providing an extra layer of insulation. Examples of these include anise hyssop (Agastache), butterfly weed (Asclepias), lavender, Russian sage (Perovskia), coral bells (Heuchera), foam flowers (Tiarella) and foamy bells (Heucherella).

Wait to cut back the foliage of Epimedium rubrum until spring.

WAIT to cut back low-growing semi-evergreen or evergreen perennials.
Barrenwort (Epimedium) and moss phlox (Phlox subulata) are evergreen groundcovers that remain green through all but the harshest of winters. Wait to prune out winter-damaged foliage in spring. Sedges (Carex) form pleasing mounds of evergreen foliage. Clean these in spring by using hands donned with dishwashing gloves to comb through foliage to remove brown leaves. The leathery, lush green foliage of hellebores contribute rich color to the winter landscape, but should be removed before new growth begins in spring.

Joe-pye weed and switchgrass are a pretty combo that add winter interest to the landscape.

WAIT to cut back perennials that add interest to the winter landscape.
Why not leave some perennials standing that contribute appeal to the winter garden? Many ornamental grasses stand up to all but the wettest, heaviest snows, providing structure in the winter garden. The tall stiff stems of Joe-Pye weed (Eupatorium maculatum ‘Gateway’), blackened seed heads of false blue indigo (Baptisia australis), flat-topped flower clusters of sedum, and spent orbs of globe thistle (Echinops ritro) and alliums are all delightful dusted with snow.

Cut back the foliage of phlox and other perennials prone to powdery mildew and don’t add it to the compost bin.

CUT BACK perennials with disease or insect problems to reduce the chance they’ll be back next year.
Remove all the plant debris from garden phlox, bee balm and peonies to reduce the risk of powdery mildew overwintering in the garden. Cut back the foliage of black-eyed Susan if they were infected with leaf spot; remove the old leaves of bearded irises to eliminate iris borers that spend the winter as eggs in plant debris.

If hostas were damaged by slugs, leaving behind holey leaves and slime trails, clean out all the foliage to eliminate their winter vacation homes and to expose their eggs to hungry frogs and toads.

The seed pods of Baptisia australis spread seeds across the garden.

CUT BACK perennials that self-seed if self-seeding is unwanted.
Some plants spread their seeds with abandon across the landscape. As pretty as Joe-pye weed is in the winter garden, it may cast seeds that fill next year’s garden with seedlings. The most seedlings occur in gardens without mulch. Cup plant and false blue indigo are other examples of plants that generously share their seeds. Even if you don’t cut these perennials down to the ground, at least remove their seed heads or seed pods before they disperse their seeds about the garden.

Are you a tidy gardener who cuts everything back; are you a leave it all standing gardener; or do you garden somewhere in the middle, like me?

Garden with me!


Note: A portion of this post was originally written for my weekly column in the Chicago Daily Herald.






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