Flowers are the ultimate crowning glory of so many ornamental plants but, in many cases, removing the dead blooms once they’ve finished is key to maintaining good health and to encourage more flowers. In the summer, the most important things to deadhead are bedding plants and bush roses as they have the ability to produce more side shoots which will carry further flowers at their tips.
Without such deadheading the plants will usually go on to produce seed. And it is this which is the priority for plants – not simply to provide you with pretty blooms. As soon as the petals start to fade, the flower will stop being attractive and will begin converting into a seed bearing structure. This occurs by the production of a range of chemicals and ethylene gas which causes the maturing of the tissues and generally suppresses the production of further flower buds. The process of seed production also takes energy in the form of sugars from the plant tissues which could otherwise be used for other types of growth including sideshoots that could carry flowers.
When to deadhead flowers
Plants which provide a continuous supply of flowers in summer really benefit from being deadheaded regularly – every few days – to prevent the supression of new flowerbud development. This is done by removing the previously coloured portion of the flower, just behind where the petals are attached. There is often a notable bulge inside or behind the flower which indicates the position of the ovary where the seeds would develop. Pinching off the old flower, either between thumb and forefinger, or using scissors or snips, is all that is required.
The remains of the flower stalk – in most cases still green – retains the ability to produce sugars for the plant by photosynthesis. It is best to let this turn yellow and drop off naturally. This is particularly important with bulbous and tuberous species – in particular spring-flowering bulbs. In summer, you may feel that such old flower stalks are unsightly, in which case they can be cut back down to the point where they join the main stem of the plant.
On cluster-flowered bush and climbing roses, you may find that you need to pinch or remove the individual faded flowers one at a time as the petals go over. Eventually all the buds will have opened, and when the last one flower fades on that particular cluster, the supporting stem can be cut back by around half its length, to just above a leaf. This will encourage the formation of sideshoots that may go on to produce flowers at their tips. On large, single-flowered roses, the stem can be cut back by half as soon as the single bloom fades.
On bedding plants and annual flowers, removing faded blooms is necessary to keep a succession of blooms coming. Those that are used for cut flowers, such as sweet peas in particular, should be picked regularly. Some bedding plants have been bred to be ‘sterile’ – ie they don’t produce seed – which means that they only require deadheading for the ‘look’ of the plant. Faded brown petals can be visually unattractive.
When NOT to deadhead flowers
There are a number of occasions where you may not want to deadhead the old flower. This is particularly the case in podded and fruiting crops where the desired, usable part will develop from the remains of the faded flower. Tomatoes, peas and beans, as well as courgettes and a whole host of other ‘fruits’ form in this way. Tree fruit, such as apples and plums, as well as bush fruit and cane crops should also have their flowers left in place as they fade for the fruit to form.
When it comes to ornamentals you may wish to leave some of the faded flowers to remain so that seed can develop. This is particularly the case where you want to collect seed once fully ripe to allow you to grow more of that plant. If the plant is a biennial, herbaceous perennial or woody plant, it is wise to limit such seed formation to just a few old flowers so that only a small amount of energy is used by the plant for its formation. If you leave too many seeds to form, the amount of energy used can weaken the plant or reduce flowering in the subsequent year.
From mid to late summer, there are a number of herbaceous perennials and ornamental grasses that produce flowers that are followed by decorative seedheads. These can be left for display and to provide interest late into the autumn and, in some instances, on into the winter months. The same can be said for ornamental plants, including woody trees and shrubs, which produce decorative berries to create invaluable autumn and early winter displays
Such seedheads and autumn berries are also useful sources of food for birds and some other garden wildlife to help them survive the winter.