Tip of the Week — 5/26/09

Posted in Gardening Tips on May 26 2009, by Sonia Uyterhoeven

It’s Time for the Chelsea Chop

Sonia Uyterhoeven is Gardener for Public Education at The New York Botanical Garden. Join her each weekend for home gardening demonstrations on a variety of topics in the Home Gardening Center.

For those of you who grow sweet peas from seed, you will know from experience that once the seedlings reach 4–6 inches tall, you need to pinch them back to approximately half their height to encourage good branching. Some people pinch just once, other pinch twice— like most things in gardening, method is often based on personal preference.

If pinching seedlings with your fingertips sounds too dainty, then just wait until late May or early June, the time to grab your sheers or pruners and try them out in the garden on a larger and more satisfying scale…but not on your sweet peas, please.

In England they call cutting back perennials the “Chelsea Chop.” This is because the time for cutting back perennials lands on the same week of the famous Chelsea Flower show (the third week of May). Cutting back some (not all) perennials early in the season encourages lateral growth and produces nice and bushy (if not slightly shorter) plants.

What are some candidates for this treatment?
Sedums (Sedum), pictured: Chop them in half in late May and you will prevent them from opening up and falling over later in the season.
Montauk daisies (Nipponanthemum): They often relish being chopped twice in the season, which keeps them from splitting open once they are in bloom.
Asters (Aster) and chrysanthemums (Chrysanthemum): If you are meticulous and have just a few, you can pinch them by hand by taking your thumb and forefinger and pinching off the growing tip of the plant (generally a half inch to 2 inches from the top). Let the plant grow a couple weeks until it puts on 2 or 3 nodes and then pinch again. For those of you who are as impatient as I am, just chop them in half once and then walk away.

Russian sage (Perovskia), pictured, hardy hibiscus (Hibiscus), and Joe Pye weed (Eupatorium): Cutting back the Russian sage early in the season ensures that it will stand tall and proud through the summer. The hardy hibiscus and Joe Pye weed, with all their late-season glory, sometimes take up too much room in the cramped garden space; cutting back helps contain them.

If you lack severe surgical impulses, gentler options are available. If you have a sedum that is starting to flop, often lifting and dividing it in the early spring is enough the help it retain its shape. There are always new cultivars on the market that are nice and compact—we know this from selections of asters, golden rods (Solidago), and many others.

Finally, there is nothing wrong with getting out into the garden early in the season to stake your perennials with peony hoops, bamboo stakes, and a large armory of garden gadgets that will help keep them in their space. Just remember that with staking it is best to get out early, before the plants start to bend out of shape.