What is the Chelsea Chop? A new hairdo or a fancy cut of meat? Nope, it’s just a pruning technique borrowed from the Brits. By cutting back leggy perennials by late spring or early summer, you can have more flowers on a fuller-looking plant.
The name “Chelsea Chop” comes from Great Britain because they do it around the time of the annual Chelsea Flower Show in May. However, for many areas, the timing is simply late spring or early summer. For me, it should be called the “4th of July Chop” because cutting the plants any later than that won’t give them enough time to recover and blossom before fall.
The whole idea is that one hour of pruning now would result in three more weeks of flowers at the end of their season! As well as extending the blooming season, you are controlling the growth and shape of your perennials for a better-looking, fuller, more compact plant. This pruning technique is especially suited to perennials to get too tall and leggy such as phlox, aster, and sedum.
Photo: Time for the Chelsea chop otherwise these plants get too tall and floppy.
I ruthlessly chop off the top 1/3 of 1/2 of the New England asters and tall phlox in my front flowerbeds because they get so tall we can’t see out of the windows! I am a little more selective in the other beds, cutting back only about half the plants in a clump, leaving a few to grow tall and blossom earlier. The shorter ones help to support the leggy ones, lessening the need for staking, and hide their “naked ankles”, the leafless stems at the base of the taller plants.
Before: The rapidly growing asters and phlox have obscured the dark-leaved ligularia.
After: Now the ligularia has a fighting chance. I left a few tall asters near the back of the bed to blossom earlier than the newly cut plants in front.
I usually just use my trusty kitchen shears to make random sharp cuts but you can use pruners, loppers, or even hedge clippers to get the job done faster.
Before: Phlox take over in front of the shed and get so tall and floppy it can be a challenge to open the door! They also overtake the other plantings.
After: Now you can see the container that was hidden by the growing phlox plants. I left a row of tall ones in the back to blossom first. They have the shed to lean on for support and the shorter plants in front of them will hide their naked ankles.
Pink asters are in short supply in my garden so I take advantage of the opportunity to make more.
If you are as frugal as I am, save some of the cuttings to root and make new plants! New England asters and phlox cuttings placed in a glass of water will produce new roots in no time. They can be potted up to share or planted out in the garden where they often bloom the first year.
The Chelsea chop is best done on late summer or fall bloomers like rudbeckias, helenium, goldenrod, asters, phlox, marguerites, chrysanthemums, and nepeta. Since it encourages branching, the plants will be shorter, more compact, and have more flowers. By leaving a few tall ones to bloom earlier you can extend the bloom time. Give it a try!
Read more about how to care for a perennial garden.