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Report From An Opinionated Gardener – September 3

Blog disclaimer: Although this opinionated gardener has definite thoughts about what should be cut back in the fall, and which plants should be left untouched until spring, she also knows that in gardening and life there is no one right way. Not that this changes my talk or walk on this subject.

I received an email recently that said the following: “My friend and I disagree over hard pruning late in the season. She will hard prune buddleia, hydrangea, gaillardia, penstemon, salvia, etc any time of the year. She removes lots of leaves and stems, taking them all to the ground. I was under the impression that the plants need the leaves and stems for photosynthesis.  We thought it best to consult you to learn if hard pruning this late in the season is an ok practice.  I typically prune hard in late March…

I replied that I think most perennials can be cut to the ground at the end of the summer, particularly early flowering types like salvia and peonies that have had the entire season to build up their energy stores.

I personally use the rule that if a perennial plant looks green and healthy at this time of year, the leaves are clearly still doing a job for that plant (photosynthesis) and I leave those in the garden. If the foliage is looking yellowish, brown or worse, I cut the plant back. So I’ll be cutting things like the yellowing bleeding heart back in early July, peonies in early September etc. But the Heucheras and Campanulas that look great right now I’ll leave until later or even through the winter.

I also leave woody plants because they store carbohydrates in their stems that they use to survive the winter – the root systems  take the sugars from the stems for root growth in the fall, winter survival and even to begin the process of breaking dormancy in early spring. So the butterfly bush, roses, and hydrangeas I leave until April or even early May.

Another reason to leave these plants is that it’s likely that they will have some die-back over the winter, and by cutting them down and dying back, the plant ends up even shorter. For roses and hydrangeas this always means fewer flowers.

My guess is that my correspondent’s friend has not seen her plants dying because she’s cutting them down, and if her hydrangeas are the types that bloom on new growth, she hasn’t prohibited their flowering. If she has more than one of any particular plant and is curious, she might cut one down and leave the other in order to better judge this practice.

Ultimately things work well if we all look at what we’re doing/believing with open, curious and critical eyes. After considering all that we’ve observed, we are then prepared to say, “This is what I think and do. It might, or might not, work for you.”

I could cut this LimeLight hydrangea back hard and it would still flower next summer...but I love how the flowers fade from white to green and pink all fall. Similarly, I love the red blood grass well into October, and the Heucheras that remain attractive through most of the winter. The asters in this bed I choose to leave so that wildlife can eat the seeds. And the golden rod on the right? That I'm just too lazy to cut down.

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