Chop, chop
THE Chelsea Flower Show returns this week to its traditional May slot after two years adrift due to Covid.
Last year it took place in September resulting in a very different palette of plants and a somewhat autumnal feel. So this week we can expect the return of Chelsea floral favourites such as aquilegias, irises, roses, peonies, foxgloves, anthriscus and alliums.
The May slot is also a handy reminder for a gardening technique known as the Chelsea chop. This involves cutting back the growth of herbaceous perennials and is so called because the end of May, or Chelsea Flower Show Week, is when gardeners begin to do this.
So why do we do this and what exactly does it entail? The purpose is to make the plant more compact and floriferous. By pruning it back now, you encourage lots of side shoots which makes the plant bushier and produces more flower buds, though somewhat smaller flowers.
A big advantage is that the plants are sturdier and shorter so will not require staking. This is particularly handy for front of border plants so they do not flop over onto the pathway or lawn.
It’s not suitable for all perennials but it works very well with later flowering ones such as sedum, phlox, solidago, heleniums, rudbeckia, penstemons, echinacea, perennial sunflowers and anthemis. It also has the effect of delaying flowering so if you’re really smart, you might just chop back some of the clumps but leave others as is – this way you will achieve different heights and extend the flowering season. You can even play around with one plant, cutting some of the stems and leaving others as is.
How do you do it? Just with a sharp pair of garden shears or secateurs and cut back by a third or half of the stems. In my own plot, I’ll be doing that shortly with nepeta. It’s a plant I love for its aromatic foliage, lavender blue flowers and ability to quickly create volume in bare spots.
However, it can get a bit sprawly by late summer and by some pathways I would prefer it to be neater, so I’ll cut back current growth by 50%.
It’s already throwing out long stems so it’s the right time here, but judge for yourself – if you are in colder, northern areas where growth is only commencing, it may be a little early to do this job and could be left until mid June when growth is flourishing.
If you fancy, your clippings will make good softwood cuttings. Tender clippings will develop root systems quickly.
Cuttings should be around 4 inches long, trimming just below a leaf node and removing the lower leaves to help them retain water.
Place in cutting compost, water in and cover with a plastic bag for humidity and place somewhere warm and bright.
Remove the bag twice a week to air the plant and, all being well, they will root within two to four weeks.