10/26/09
Cutting Back Perennials in the Garden
I am often asked: “When is the best time to cut back my perennials – right now in the fall, or wait until spring?” In my opinion, the short and easy answer is: “Spring”. If you really want to talk about it though, I’ll have to start with “Well, it depends…”.
Being a bit of a procrastinator in general, I don’t really get in a rush to do many things, let alone cut the tired, brown foliage of my perennial plants back to their crowns in late fall. Usually by now I’m ready to pack away the garden tools and pick up a good book and a warm mug of something to drink and hole up somewhere cozy for the long winter. I do have a few reasons to justify my gardening laziness in this case, however! But before I get to those, here is the most important exception to my ‘laziness is good’ theme that you should be aware of: If you have perennial plants with foliar fungal or disease problems, such as powdery mildew (whitish, powdery film on the leaves, especially common in damp years), it is best not to leave these plants laying around your garden as a potential source to re-infect next year’s plants. To minimize this chance, cut the foliage of these plants back very close to the ground this fall and dispose of it by burning or in the trash, and not in your compost pile.
And now for the reasons you may want to wait until spring to cut back your perennials:  Sparing perennials from the shears this fall gives them every last moment they can get to photosynthesize and continue to send energy into strengthening their root systems for winter. I could not advocate cutting back perennials by a certain, finite date every fall because, and here’s some more of that “it depends” part, we never know each year when we’re going to get that hard frost that signals the bitter end to photosynthesizing fun. Why would you want to cut actively growing plants back any time before then?- Leaving the stems, dried leaves and seed heads of perennial plants alone until spring means the plants will catch more blowing snow around their crowns, taking advantage of a little natural insulation. That’s right, the snow layer actually provides temperature-moderating protection from the freeze/thaw cycles of our unpredictable winters. We gardeners should WANT to get a lot of snow!
- Leaving the seed heads of perennial plants standing proudly and bravely in the snow provides visual winter interest in the garden, and also food for several types of wild birds. Birds especially appreciate the seed of Echinacea (Purple Coneflower), Rudbeckia (Black Eyed Susan), Eupatorium (Joe Pye Weed), and Liatris (Spike Gayfeather), among others.
- Last but not least, by the time spring comes, the work of cutting back perennials has become a lot less work. The leaves and stems are dried up and often broken off by the weight of the snow, and most perennial plants need just a gentle raking off with a leaf rake right before or just as their new sprouts are peeking out of the ground to get them ready to grow!
Of course, if you are a gardener who appreciates a clean, neat winter landscape and likes to cut back and clean up your perennials in the fall to get ahead of the spring rush, that is fine, and keep up the good work! (just don’t do the work too early in fall when plants may still be growing). The best time to do something is often whenever you can simply find the time! By Stephanie Girgen
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