Well, summer is here. Heat and thunderstorms confirm this. And your summer flowers should be full of bloom. If they are in pots, regular watering and feeding will keep them flowering. But there is one more job that we need to do: deadheading.
There are two main reasons for doing this. Firstly it keeps plants looking tidy. Plants always look better if covered in pristine blooms without the distraction of brown or discoloured petals. But, more importantly, it prevents plants from setting seed. Most plants have only one thing on their mind (if they have minds), and that is to produce seeds so that they can produce the next generation of plants. Most of the plants we grow in our gardens have been carefully selected by gardeners and plant breeders and some of your bedding plants, like the latest diascias or petunias, may not actually be able to set seeds. They have been created so they do not set seed and so bloom continually. Even so, they may benefit from a tidy-up.
But most plants will set seed and if the plants manage to produce seed pods their job is done and they will stop flowering. As gardeners we want the flowers to keep on coming so we remove the faded flowers, as soon as the petals fade, to encourage more blooms.
The most obvious examples are annual and bedding plants. Cosmos, zinnias, marigolds and many more can have their flowering season extended for months if they are deadheaded. It is best to do this every few days if possible. It is no use leaving the dead flowers to develop into seeds and do the job once a month – the damage will be done. It is especially important for sweet peas which is why it is perfectly acceptable to cut a bunch twice a week from your plants. If you let just a few pods develop it will mean your plants lose vigour and stop blooming very quickly.
Few people bother to deadhead shrubs and it is not always practical but it is definitely worth removing the old flowerheads from buddleias. It makes the plants look tidy but also prevents seed production and encourages a flush of later flowers.
Roses also benefit from deadheading and once the last petals have dropped from a bloom or cluster of flowers, you should prune off the stem. How far down you cut is not crucial – but it affects how quickly the plant will rebloom. If you trim back just a little, down to the top full-sized leaf (below) you will get the quickest rebloom. But cut back a little more, reducing the new stem by about half, you will get larger blooms but a little later. What is important is that you do something!
When it comes to herbaceous plants, if you cut back the stems on lupins and delphiniums once the last flower has faded you will get more, shorter stems of flowers from the base. Not all plants will produce more blooms. If you remove the old flowers on peonies (just the old flowers so that all leaves remain) it will keep the plants tidy but will not encourage more blooms this season.
Don’t think of deadheading as a chore. It is a chance to get close to your plants and as you do the job you will also notice how the plant is growing and spot the early signs of pest or disease too.