The first spring in our house (2010) I proudly planned, plotted and planted 650 native perennial plants. I put a lot of thought into plant height, bloom time and color; creating a diverse, year-long beneficial beauty bed.
As that summer was coming to an end I quickly realized I had no idea when and if I was supposed to cut back my plants. I went down a goggle rabbit hole searching for "what day are you supposed to cut back perennials in zone 6b?" I was looking for an exact date, this still makes me laugh out loud when thinking back on my naiveté. I emerged from my deep dive more confused than when I entered; half of the articles argued for cutting back perennials in the fall while the others stood by spring as the best season for trimming the dead.
After 13 years of trials and tribulations I still do not have a definitive answer as to when to cut back perennials. If I HAD to choose just one season, I would say that spring is the best time for pruning off the dead. The world, much like the answer to this question, is not black and white; it has a more nuanced and colorful approach. I am no expert in this field, but here are some concepts that have rang true for me over the years.
Benefits to Cutting Back Perennials in the Fall
Neat and tidy. By cutting back all of the dead growth in the fall, you will have your beds looking manicured and in order at the end of the season.
Removing diseases. Some plants will develop pests and diseases that can overwinter and return in the spring. By removing the inflicted foliage in the fall, you can combat these problems.
These ideas were very appealing to me my first year leading me to the decision to cut back in the fall. It felt good to have the work done and behind me; earning my winter's rest. If you choose this route and cut back in the fall, keep this in mind:
Make sure you prune back the dead AFTER the first frost. If you cut them back too early, the plants will have time to create new growth and the onset of winter can shock them to the point of no return (just ask my beloved Pink Muhly hair grass;( I still miss their pink, punk rock presence in the bed) Do your plants a favor and let Jack Frost pay you a visit before you get out there with the clippers.
Benefits to Cutting Back Perennials in the Spring
Providing food and shelter for wildlife. Spent flowerheads, such as echinacea, provide seeds that allow birds to naturally forage for their food. Beneficial insects can hunker down for the winter in the hollow stems of dead growth. And critters can be sheltered from the elements in any brush left behind.
Provide groundcover. By allowing the dead plants to stay put over the winter, they safeguard the soil from being bare and exposed to weather and winds. They also provide protection and insulation; like a winter's coat.
My Current Approach; a hybrid solution
I used to strive to keep my beds clean and orderly; leaving the dead behind was an eye sore for me that was hard to get past. Once I learned of the benefits this provided to insects and wildlife; my lens shifted to see the beauty in the brown brush; allowing my brain to get behind leaving the plants standing until spring.
While now I opt to leave most of my perennials standing until spring, I do cut down our Hostas in the fall; they become a wet, mushy mess that may harbor slug eggs and other problem creatures. Otherwise, I limit my cutting back only to the diseased and pest infested plants in the fall, removing them from the area and burning to prevent further spreading.
In the spring, I carefully look for new green growth; signifying the plant is ready to reemerge. This is my cue to cut back the dead stalks, taking care not to any new green growth. This allows the plant to focus its energy on producing this year's bounty. Here in Zone 6b we hardly had any winter at all, and as you can see in this photo, we are starting to see new growth at the end of February!
Midsummer, I may cut back some plants to encourage new, bushy growth. Some times this will just be as simple as dead heading spent flower tops, promoting many new blooms before the end of the season. Other times I may take a more drastic approach and cut the plant back to only 2-3" of growth. Last year I planted some new perennials that had weak, straggly stems. Cutting them back almost to the ground encouraged them to resprout with a studier, fuller plant in the same season.
After three seasons of yardwork and gardening; I become burned out by the end of October, ready to retreat to the house for winter hibernation. When spring emerges, I am excited to get outside again; soaking up the warm sun and getting my hands and feet back into the dirt. It just makes sense for me to save the laborious chore of cleaning out the perennial beds for when I am refreshed, recharged and looking forward to being outside in the spring.
What time of the year do you cut back your perennials? Do you a set season, or more of a hybrid approach like me? I would love to hear from you about your perennial care practice, comment below and tell us your take.