Laidback Gardener Tip of the Day

Perennials: No Fall Cleanup Required!

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Why in the world would you cut back the leaves of a perennial in the fall: its dying leaves are an important part of its survival strategy.

The idea of “cleaning up” your perennials in the fall should have died out decades ago. It’s never been necessary and in fact the tradition of cutting perennials to the ground in late autumn is even harmful. You’ll find that perennials grow better if you simply leave them alone in the fall.

Why?

Because, on one side, the dead and dying leaves help protect the plant not only from the cold, but especially from freezing and thawing (usually much more deadly than cold itself). Dead leaves are a natural insulator.

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The best fertilizer for any plant is its own decomposing leaves.

But also, remember a detail that can’t be emphasized enough: the best fertilizer for any plant is its own foliage. Its leaves contain exactly the minerals the plant needs to grow and bloom well. So Mother Nature devised a wonderful system whereby the old leaves die, but decompose on the spot to feed the plant the following year. Millions of years went into developing this self-sustaining system… yet so many gardeners still think they know better than Mother Nature and cut the leaves off.

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Cut off the plant’s leaves and you’ll have to replace the minerals lost with expensive fertilizer!

Think of it this way: if you remove the plant’s dying leaves, you’ve made the soil the plant grows in poorer, so you’ll have replace the missing minerals with fertilizer next spring. So you just added two useless activities to your list of things to do in the garden (cut off perennial leaves in the fall, apply fertilizer in the spring) and, worse yet, you have to pay for the fertilizer!

Of course, there are gardeners who will say they cut the leaves off in the fall so they won’t have to do so in the spring, that it is more pleasant to pick up relatively dry leaves (in the fall) than leaves soaked by a long winter under the snow (in the spring)… but that’s a sign that they still don’t understand Mother Nature.

The leaves of perennials decompose during the winter. They are not there in spring or, if still present, are in a state of decomposition so advanced that if you let them continue, there will literally be nothing left before summer even begins.

All that’s left to “clean up” in the spring (and only on some perennials) are the dead flower stalks. They have, in many cases, been feeding the local bird population over the winter, but that role is over by spring. So, when the snow melts, if these stems are still standing and if they bother you, simply snap them off at the base and place them on the ground at the base of the mother plant. That way they will continue their role of feeding momma and will decompose in their turn over the summer.

Good Bugs Versus Bad

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The praying mantis often lays its eggs on flower stalks. Fall cleanup can therefore eliminate this beneficial insect from the garden.

Moreover, often beneficial insects overwinter in the dead leaves and hollow stems of your perennials. If you remove them in the fall, it’s like welcoming undesirable insects into your garden. Let the leaves and stems decompose on the spot and the beneficials will already present when the bad bugs awaken.

In conclusion, the fall cleanup of perennials is a waste of time and it is even harmful. So why bother? Instead, take a laidback attitude and let Ma Nature do her thing!

One Exception

I know of only one exception to the rule that it is better not to cut back the foliage perennials in fall: the bearded iris (Iris x germanica).

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Cut back bearded iris leaves after the first frost.

If you’ve had problems in the past with iris borer (Macronoctua onusta), it would be wise cut back the foliage in the fall. Its eggs overwinter on leaves and stems of the mother plant, so by cutting the leaves back and destroying them, you can help reduce or even eliminate borers from your garden.

However, most gardeners don’t even get this right: they cut back iris leaves too early in the season. Wait until after the first frost. That’s because the iris borer moth remains active until then. If you cut back the foliage earlier in the fall, it will simply come back and lay more eggs on whatever bit of iris that is still above the ground. If you cut back the foliage after the first frost, though, no more eggs will be laid and this can indeed help prevent borer damage the following spring.

I found an even more laidback solution, though: I eliminated bearded irises from my flower beds and only now only grow irises that are resistant to iris borer: Siberian iris (I. sibirica), blue flag iris (I. versicolor) and variegated iris (I. pallida ‘Variegata’), just to name a few. As a result, I can simply let my irises take care of themselves in the fall: one more proof that a laidback attitude to gardening really is the best way to go!

Larry Hodgson is one of Canada’s best-known garden communicators. He has notably been editor-in-chief of HousePlant Magazine, Fleurs, Plantes et Jardins, À Fleur de Pot and Houseplant Forum magazines and is currently the garden correspondent for Le Soleil and radio garden commentator for CKIA-FM Radio. He has written for many garden publications in both the United States and Canada, including Canadian Gardening, Harrowsmith, Horticulture, Fine Gardening and Organic Gardening. He also speaks frequently to horticultural groups throughout Canada and the U.S. His book credits include The Garden Lover’s Guide to Canada, Complete Guide to Houseplants, Making the Most of Shade, Perennials for Every Purpose, Annuals for Every Purpose, and Houseplants for Dummies, as well as nearly 60 other titles in English and French. He is a past president of the Garden Writers Association (now Garden Communicators International) and the winner of the prestigious 2006 Garden Media Promoter Award offered by the Perennial Plant Association. He resides in Quebec City, Quebec, Canada.

13 comments on “Perennials: No Fall Cleanup Required!

  1. Trish Hardman

    Now you’re talking my language! Neighbours must think my garden is so messy and wild, but it is tended with nature and her creatures in mind😊. Thank you for clarifying that point.

  2. Marion Baber

    Sounds reasonable to me,except how about rose beds ? Bad things overwinter under them, blackspot,mites,ect.
    I grow daylilies and this works good for them .
    Thanks for the artical ,Ive got enough to do in the fall!!

    • Roses are not perennials, so it’s a different story. I must admit I find most roses too much work and don’t grow many of them. The ones I do grow are the extra hardy, disease resistant types, so they don’t need anything special in the way of fall care.

      • Marion Baber

        THANKS, I’M GOING TO TRY IT IN MY DAYLILIY BEDS THIS YEAR. I USUALLY CLEAN THEM IN LATE WINTER .

  3. This has been y practice in later years.. Leaving the garden to compost itself I do though cut back some things, but leave the cut material on the garden bed. Chopped up. I always think the same it is material from the plant itself and so should return to the soil. One large long flower bed is right along the sidewalk in front of my hoe. My neigbhours used to think, especially one of them that I should clean it right up Nice and tidy. But they have gotten used to it being “messy” no it has become one of the nicest flowering beds in the neigbhourhood. Plants in bloom from early srping to late fall. Nice colour even now from the leaves on some bushes.

  4. Sandra Clarke

    I have 2-3 inches of mulch on my beds. Will the decomposing plants be of benefit through the mulch?

    • Of course! The presence or absence of mulch is not a factor. As the plants decompose, the minerals released will simply leach downwards, through the mulch, to the roots below, thus feeding the plants.

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