Carol Klein explains why vivid dahlias are the stars of autumn
They’re a gay and gaudy bunch, but that’s their strength as mellow autumn hues start to creep in
‘New varieties are publicised with panache and much sought after by those in the know’
The brightest stars in the garden at Glebe Cottage are our dahlias. They’ve been glowing for weeks now and will probably continue their vivid show right through to late autumn. Had they been grown here by some of our predecessors in the 1930s and 1940s they would probably have been confined to the vegetable patch, their flowers cut for the house or primped and perfected for the village flower show.
Times change and the dahlia’s image has undergone a rebranding. They have to be one of the most fashionable flowers around now and new varieties are publicised with panache and much sought after by those in the know.
On their colourful stands at various flower shows, the National Dahlia Society include new varieties as well as tried and trusted ones.
At one time the dahlia might have been considered vulgar; it’s certainly not shy and retiring. There are a few subtle dahlias but for the most part, they’re a gay and gaudy bunch. That’s their strength: As mellow autumnal hues start to creep in to soften the bright palette of summer’s flowers, dahlias provide a reprise.
The brilliant red of ‘Bishop of Llandaff’, not to mention the burnt oranges and soft apricots of some of his children together with the vibrant purples and retina-searing magentas of big cactus show varieties, stand out against the soft biscuits and olive-green of fading perennials and grasses.
Dahlias come originally from Mexico where they had other uses than their considerable ornamental charms. In common with other Central and South American plants, including the potato, dahlias have tubers which allow them to store energy, starch and sugar underground through the cold winters, often high up in the mountains.
The continental climate with cold winters and hot summers means they’re able to grow rapidly, flowering and setting seed before withdrawing underground to rest until the following year.
Our maritime climate is different – although we can grow dahlias successfully, we need to
give them special treatment. Although many gardeners are now experimenting with leaving their dahlias in the ground, usually covered with mounds of soil to protect the tubers from frost, the safest way to safeguard tubers is to lift them, preferably when the first frost has blackened their stems.
Cut any remaining stems down to a few inches, shake off excess soil – if it’s wet and/ or your soil is heavy, turn the tubers upside down to allow any excess moisture to drain away. When they’re dry, but before they start to shrivel, store them in dry compost or bark.
Make more plants
They’ll be happy in any frost-free place, the garage, in a shed or under the greenhouse bench. Check them from time to time and remove any that may be rotting. Pot them up if there’s space and bring them into growth by watering gently.
It’s at this stage you can make more by taking basal cuttings. On bigger plants with several basal shoots, slide a sharp knife into the base of the shoot as close to the tubers as you can without damaging them. Remove a leaf or two and nip out the top of the shoot.
The other way to make more plants is to grow from seed. The most prolific seed setters will always be single. Eventually seed heads turn brown and papery and when they’re thoroughly dry they can be severed from the plant and the slender black seeds can be separated from their cases.
Left, spiky drama from cactus dahlia ‘Yellow Star’ and, right, the daddy of them all, ‘Bishop of Llandaff’