During late spring, you can experiment with the 'Chelsea chop', cutting back your perennials to improve their flowering performance. This pruning method is carried out in late May, around the time of the RHS Chelsea Flower Show, and can be done on a wide range of perennials, including phlox, penstemons and sedums.


11 plants to Chelsea chop

Doing the 'Chelsea chop' can delay the flowering of perennials by four to six weeks. You can either prune all the stems on a clump, which delays all the flowers, or just half of them, which spreads the plant's flowering over a longer period.

Chopping entire plants is useful in a border where all the plants bloom at the same time, because it extends the display. Pruning back half the stems means that some will still flower in their natural season, while the rest will take over when the first ones have finished.

More pruning and trimming content:

In this video, Monty Don shows how to do the Chelsea Chop on lysimachias and heleniums.

Discover our top tips for carrying out the Chelsea chop.

Use sharp, clean secateurs

Pruning phlox with secateurs

Use sharp, clean secateurs to cut back the stems of perennials such as phlox, pictured, making a sloping cut just above a leaf joint.

Decide how to cut

Pruning sedum

The quickest option is to simply cut back all the stems on the clump by one third, or by half for leggy plants. Alternatively, you could cut back the stems on one side, or cut back every other stem throughout the clump.

Which plants to try

Vivid-pink phlox blooms

You can try the Chelsea chop on a range of vigorous perennials to ensure your borders bloom over a long period – try it on achillea, asters, campanula, echinacea, helenium and more.

Cutting back penstemons

Cut back half of your penstemon stems in May, so you can enjoy the flowers for longer.