The Perennial Maintenance Question: When Should I Cut Back the Garden?

October 15th, 2012 § 6

Rainy-Day, Autumn Maintenance in My Wildflower Walk: Cutting Back Withered Perennials & Removing Weeds

Ah, October. One minute it’s freezing cold and you’re pulling on the wooly socks, and the next you’re stripping to your t-shirt and slathering on the sunscreen. I wonder… Do gardeners in other regions talk about the weather as much as the folks here in New England? A few years back, I was enjoying a live Lewis Black rant on meteorological events, when the comedian turned his attention to the peculiar phenomenon known as New England weather. Only in Boston, he fumed, can one experience: “…thunder, lightening and snow— together”. The audience groaned in unison and filled the room with nervous laughter. It’s true: no matter what the season, you just never can tell what’s in store in our unpredictable climate. Mother Nature certainly has a varied bag of tricks reserved for those of us living in the northeast, and last year, she brewed up a nasty Halloween blizzard; knocking out the power for days and canceling trick or treating (visit last year’s post for photos of the beautiful horror). So with all of this zany New England weather, deciding when to put what “to bed” in  the garden can be a bit of a challenge.

In Mid-October, Seed Pods and Dried Flower Heads Add Textural Interest & Contrast in a Garden Filled with Autumn Foliage (Doctor Woo Relishes an Afternoon of Fall Mouse-Hunting while I Spread Mulch and Tidy Up the Garden)

Last year’s early snowfall caught many gardeners —including this one— by complete surprise. Ornamental grasses, textural seed heads and dried flowers were all crushed by a heavy, white blanket. It was the first time in many years that my garden shut down early. Normally, hoar frosts and light, November snow squalls add seasonal beauty to the garden; tracing skeletal forms in delicate, glistening layers of ice crystal and white lace. For this reason, as well as a desire to attract wildlife, I prefer to leave most textural plants —such as Rudbeckia, Coreopsis, Eupatorium, Miscanthus, Echinacea, Rodgersia, and Asters to name a few— standing throughout the winter months, and cut back whatever remains of these perennials in early spring. However there are some perennials I trim back fairly soon; such as the “melter” plants, including Hosta and Ligularia, and the “scraggle dogs”, like Aruncus, Phlox maculata and Heliopsis. After the first hard frost, I try to critically evaluate the landscape and cut back perennials that no longer provide sustenance to wildlife or add structure, texture or color to the overall garden design and composition. And although I clip back certain woody plants to within 4″ of the ground —Hydrangea arborescens, Perovskia atriplicifolia, Lespedeza thunbergii, etc— I leave most structural pruning for late winter and detailing of woody perennials for early spring.

I Prefer to Leave Certain Dried Flowers —Such as Rodgersia (Shown Above) & Astilbe— Standing in the Secret Garden, to Catch Frost, Ice and Snow. These Perennial Plants will be Cut Back in Early Spring

One of the Great Joys of Ornamental Grasses is the Winter Beauty They Provide in the Garden. Shown Here, Switch Grass (Panicum virgatum ‘Heavy Metal’) Coated in a Layer of Ice

Two of My Favorite, Architectural Flowers —Rudbeckia and Echinacea— Provide Sustenance to Overwintering Birds. Seed Producing Flowers are Always Left Standing in My Garden. What Remains will be Cut Back in Late April or Early May

Deciding which perennials to cut back when is often a matter of personal preference and garden style. The seed pods and drooping, dried flowers that one gardener thinks poetic, another might consider a terrible mess! You may like your garden neat and tidy, but in terms of protection, most perennials are quite hardy and need very little TLC. Zone marginal and newly transplanted perennials should always be cut back and mulched for winter protection, but established perennial borders are far less fussy. In my own garden, I leave most plants standing and clean up remnants in early spring. Do you have a specific question about when or what to cut back in your perennial garden? I spent the first 15 years of my professional, horticultural career maintaining gardens, and I’m happy to share what I’ve learned. Please feel free to ask about autumn perennial maintenance in the comments, below!

Garden Design & Installation: Michaela Medina Harlow

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§ 6 Responses to “The Perennial Maintenance Question: When Should I Cut Back the Garden?”

  • Andy Brown says:

    I think my garden’s scraggliness is more scraggly than poetic at the moment, but that is mainly the kitchen garden. The birds are very active in there, so I leave it be. My question would be about my shrubby quinces. They put on a wonderful and welcome red profusion first thing in the spring, but I also like the apple-sized fruit, and after a bumper crop two years ago, they have fixed hardly any fruit at all for the past two autumns. Clearing out some competition is obviously called for, but I wonder what you’d suggest as far as pruning goes. Any advice would be welcome. (I’m in Rhode Island, by the way.)

  • Michaela says:

    Hi Andy,
    When it comes to pruning Quince, you have two options. If you have only light pruning in mind you can thin and shape right after flowering (remove dead, old wood and thin some of the branches, particularly at the center or where you see crowding). Alternately, and if you would like to do more structural pruning, you may prune up to a third during winter dormancy (February or early March here in New England). Flowering Quince may also be renovate pruned entirely, although with the exception of very small shrubs, this is usually too drastic an aesthetic option in most landscapes (for those reading and unfamiliar with this term, it is used to describe a process where the entire shrub is cut back to within 6″ of the ground, to renew).
    In terms of fruit set, I have seen the variability you describe in certain older cultivars. Flower buds on Quince are easily damaged by cold. It is possible that a late cold snap or frost affected your fruit set (there were a couple such late frosts in certain areas of New England last spring). Sometimes the shrub will flower after a late frost, but produce little or no fruit. It’s also possible that something is eating the fruit before it matures (squirrels or birds, possibly).
    For specific woody plant pruning questions (as in, how to cut or where), I would suggest Lee Reich’s Pruning book, which you will find linked on the “Library” page.
    Hope this helps! ;) Michaela

  • Laurrie says:

    The panicle hydrangeas look good all winter, so I leave them, but what about serrata hydrangeas (‘Bluebird’ and ‘Preziosa’)? We had a hard freeze last week, and they are black now, so I want to cut them down to the ground just to look better. Both bloom on old and new wood, but neither bloomed this year because we had an aberrant hard freeze in late spring. I’m zone 6 Connecticut, but I am having trouble with these “hardier” mountain hydrangeas!!

    Can I prune to the ground, or should I leave them and let the leaves abscise on their own?

  • Andy Brown says:

    Michaela,

    Thanks for the feedback – that’s very helpful. I think I may try out all three options in various places! For the “renovate” pruning, what time of year is best for that? February-March?

  • Michaela says:

    Hi Laurie, If you prune to the ground you will sacrifice bloom on old wood and set the shrub back. The only Hydrangea that I prune in autumn are the smooth. I will remove spent flowers on others, but nothing more until spring. I agree that some can look very unattractive!

  • Michaela says:

    Hello again, Andy,

    I would hold off on renewal/renovation pruning until after bloom, if it is an early blooming cultivar. Have fun out there! M