Ask the RHS EXPERTS
FOR THE CHOP
Q I would like to try the ‘Chelsea chop’ – do you have any hints?
A Cutting back or shortening herbaceous perennials at the end of May can transform some flowers. Flower embryos or ‘initials’ are not yet fully developed and cutting off the stems by one third does not seriously weaken the plant. Shorn plants grow new shoots, which will flower about three weeks later than unpruned shoots, spreading the flowering period by about a month. They will also be shorter, needing less staking and support, and there are often more numerous, if slightly smaller, flowers.
Later chopping may weaken the plants and regrowth might not flower before autumn rain and frosts. Earlier pruning will make little difference to the flowering season and may weaken plants that are still recovering from winter.
Alternative methods
Q My sweet peas are covered in greenfly – is there a pesticide-free way of being rid of them?
A With a carefully directed jet of water from the hose or sprayer, you can wash away greenfly – and often keep them down until enough ladybirds, lacewing and other natural enemies arrive to keep them in check. Some sprays, such as SB Plant Invigorator, are not officially classed as pesticides as they work by physical action, smothering insects or weakening their hard exterior skeleton, rather than by toxicity. They contain materials such as soaps or carbohydrates and have minimal
