You may have heard of the ‘Chelsea Chop’ – traditionally carried out around the same time as the Chelsea flower show in late May through to early June. It is a type of pruning which limits the size, controlling when herbaceous plants flower.
Why do it? It stops plants being too tall and leggy, so they need less staking and will not flop as much later in summer. The flowers tend to be smaller but there are many more. I normally chop only half of a variety, usually the front of the clump, so the ones behind flower in the normal way so extending the season as opposed to just delaying it.
How to do? Chop back the perennial by around a third to half with shears or secateurs. By taking out the top shoots the side shoots are then encourage to grow.
What to chop? Plants that are well suited to chop include:
- Sedum – particularly the strong upright forms
- Phlox paniculata
- Campanula lactiflora
Plants not suitable are those perennials which only flower once else you will lose the flowers; varieties such as peonies, irises and aquilegias.
- Iris – once your tall bearded Iris have finished flowering, lift and divide any clumps that are overcrowded, normally every 4-5 years.
- Primrose clumps that have finished flowering can also be lifted and divided now.
- Prune early flowering clematis – such as the evergreen C. armandii, C. Montana, C. alpina and C. macropetala.
- Prune spring flowering shrubs
- Make sure all your later flowering perennials have supports in place before they flop over.
- Deadhead, deadhead and deadhead….to keep your flowers coming!