The Chelsea chop
May (or June) is the time of year to consider the Chelsea Chop, so called because it's often done around the time of the Chelsea flower show. It is simply a means of delaying the flowering of summer plants, and making the plant more compact. It can be done in a number of ways, and in fact, not just in May depending on the plant, see below. One method of using the Chelsea chop is to cut the whole plant down by about 1/3 and this delays the flowering of all of the plant and makes the plant more bushy, ( you are in effect pruning it during it's growing season.) Alternatively, you can chop some of the plant's stems by a third, but don't chop other stems on the same plant, which will stagger flowering. The unhoped part will flower first and later the Chelsea chopped part. Also, if you have two or more plants of the same variety, chop one but not the other, the options are varied.
Question : is the Chelsea Chop worth it?
I think it is; it makes the plant bushier with more flowers and, especially towards the end of the season, the plants tend to get less leggy which means it can be used to good effect on plants which tend to get lax and leggy later in summer. Below are two Nepeta late in the season, the one on the left was left alone and it appears more spread and sprawling, less bushy. The one on the right was Chelsea chopped and cut down by about a third across the whole plant and it looks bushier. As border plants get more established, and in some places bigger than is ideal, one way to stop the plant overshadowing its neighbours, is to Chelsea chop it in May or June and it will flower on shorter bushier stems. Later flowering perennials can be back in July and for early flowering plants use the Chelsea Chop in June. Some plants will benefit from being cut back hard to encourage fresh new growth or a second flush see list below
Use the Chelsea chop cuttings to propagate new plants
Lots of plants are suitable for the Chelsea Chop and it works well. In addition the soft new growth which has been cut off will make good cuttings and root very well.
Sedums are ideal to make new plants in this way. It is so easy; the tip which has been cut off can just be pushed into the ground, alongside the mother plant, and if kept moist it will root where it is, with no more effort than making a hole with a dibber. This has been done on the image to the right and the cuttings have rooted.
These cuttings are very easy to do and will make sturdy plants for next season's garden. Left over choppings from Nepeta are best placed in a small pot with a poly bag over to retain moisture, or in propagator away from sunlight.
It is good fun and worth experimenting with the Chelsea chop and cutting back some plants by a third, others just some stems by a third, or on the same plant cut some stems and not others.
Plants suitable for the early Chelsea Chop (late May early June) include:
Nepeta- Asters- Monarda-Lavandula
Echinacea purpurea - Artemisia- Sedum 'Autumn Joy'
Phlox -Helianthus- Rudbeckia
Some plants and Perennials are suitable for chopping in July to encourage a second flush of flowers. In these cases cut after flowering, and feed. A second flush is not always successful, and the flowering will not be as strong. In each case just cut of the flower head stalk which has flowered to encourage side shoots.
This is suitable for Hollyhock -Nepeta- Astrantia -Delphinium -Digitalis -Campanula- Penstemon.
Some plants and Perennials are suitable to cut back almost to the ground again after flowering in July. This is good where the foliage looks tatty and within 14-21 days new fresh foliage will shoot up which will look more attractive for the rest of the summer.
This is suitable for Alchemilla mollis Hardy Geranium (Cranesbill) Salvia