But that doesn’t stop people from growing them, either to bring a blast of colour to the garden or, as cut flowers, to illuminate the home.
Dahlias are named after the Swedish botanist, Andreas Dahl, who had an unusual use for the plant – he ate it. He thought the dahlia was better as a vegetable than a flower, and it took quite a time before gardeners got around to cultivating it for its blooms.
You can buy dahlia tubers now and plant them into five-inch pots of decent compost. Keep them warm and watered and they’ll soon produce shoots which promise superb late-season colour or offer the chance to propagate even more scintillating flowers.
If you just want your dahlias to bloom, harden off young plants before planting them outside when the threat of frost has finally vanished.
Dahlias are best grown in a well-dug soil enriched with manure and perked up with a dose of general-purpose fertiliser.
Tall varieties will need staking – a job to do before the plants go into the ground.
Once buried a few inches in their final homes and watered well, just let them grow. As they inch higher, tie them to their stakes.
If you want huge flowers, remove all but the central bud; if you want a mass of flowers, pinch out the shoot tips next month. This will encourage more side-shoots and more blooms.
When the first frost blackens the leaves, cut the stems to 8-10 inches and dig up the tubers and the soil surrounding them and pop them away in a shady, frost-free spot for a few days.
Prepare a shallow box with a mixture of garden soil and sand. Clean the tubers and put them in the box, just up to the stem. Then cut back the stems to an inch or two and store the boxes somewhere frost free and out of direct light – between 35 and 50F. Examine the tubers every few weeks, discarding any that have become soft or mouldy. The healthy survivors can be replanted in spring after the frosts have passed.