What is the chelsea chop?
This pruning technique is great for controlling tall, leaning, or otherwise large herbaceous perennials in your garden. The goal is to prevent tall garden plants from falling over when their tops are weighed down with flowers and seeds later in the season. Taller plants may also be prone to leaning after wind-storms, heavy rain, or other damage.
Tall plants that have spread to new locations over time, been planted too close to a walkway, or are significantly taller than those surrounding them in the planting may benefit from a chelsea chop.
When to chop
In late May and early June, cut back the top 1/3 to 1/2 of stems of your desired plants. This 5 minute GrowIt BuildIt video provides a good explanation of how it's done. Chelsea chopping can be especially helpful for stems along paths and garden edges (see photo). The cut stems will remain shorter than their un-pruned counterparts and grow side shoots which help hold up the tall stems in the interior of the bed.
Photo courtesy of Kate Kruesi
Pruning can prolong flowering for pollinators thereby creating a longer flowering window for a given species. Cut stems will take additional time to reach the blooming stage and will begin flowering as the other stems finish and go to seed. This has potential to lessen the impacts of "phenological mismatching" which occurs when flowering times, and pollinator emergence times don't align. In general, we recommend planting a variety of plants that bloom sequentially throughout the year to ensure that there are always floral resources available.
Choose the appropriate plants
It's important to choose plants that are likely to recover and still produce an abundance of flowers. Some species will react poorly to a chelsea chop and may not produce flowers.
In general, you'll want to choose late-blooming flowers: native sunflowers, penstemons, asters and goldenrods, joe pye weed, bee balms, and others can tolerate chelsea chopping.
Looking to learn more? Izel Native Plants does a deep dive into the world of pruning herbaceous perennials for function, form and bloomtimes.
