Gardeners are being urged to deadhead their dahlias now to keep them blooming throughout autumn, potentially right up until the first frosts.
Dahlias are among the most striking flowers in any garden, adding vibrant colour to borders just as many summer blooms start to fade. With a huge variety of shapes, colours and sizes, there is a dahlia to suit almost any outdoor space, whether grown in pots or beds.
Unlike many other flowers, dahlias can keep flowering well into the autumn months, making them especially valuable for extending colourful displays later in the season.
RHS advice on deadheading
The Royal Horticultural Society (RHS) says dahlias can continue blooming right up until the first frosts arrive, placing them among the best plants for prolonging the flowering period.
However, to enjoy their blossoms for as long as possible, there is one straightforward task worth doing regularly throughout autumn. Leaving faded flowers untouched can seem appealing as temperatures drop, but removing spent blooms can actually stimulate the plant to produce even more flowers.
This is particularly beneficial towards the end of September, when dahlias can still deliver a spectacular show.
How to deadhead correctly
Deadheading involves removing faded or dead flowers from plants, according to the RHS. It is done to keep plants “looking attractive” and to “encourage more blooms”.
Deadheading a dahlia is simple, but it is important to make the cut in the right place. Gardeners should identify flowers that have faded, wilted or lost their fresh appearance, then trace the flower stem downwards towards the foliage.
The RHS advises cutting back to a leaf joint further down the stem rather than merely snipping off the flower head. There is also a handy trick for telling a spent dahlia bloom from a new bud: flower buds tend to be rounded, whereas spent flowers become more pointed once their petals have fallen.
Frost protection and cut flowers
Dahlias are not frost-hardy and will suffer damage in freezing temperatures. Experts advise that once the foliage has been affected by the first frosts, gardeners can either leave the tubers in the ground or lift and store them in a frost-free location over winter.
Gardeners in milder regions of the UK with light, well-draining soil may choose to leave them in the ground, though this carries a higher risk of winter losses.
Deadheading is not the only way to encourage further blooms. If there is an abundance of flowers, dahlias also make excellent cut flowers for brightening up the inside of the home.
