Celebrate dahlias
Dahlia festivals are the ideal time to see these beauties in bloom
There are few sights more captivating than a colour-themed dahlia border in full throttle. And what better way to view them in all their myriad shapes and hues than at a dahlia festival? From village shows to open gardens, stately homes to nursery fields, there are dahlias blooming everywhere this month. The National Trust’s Anglesey Abbey in Cambridgeshire has a particularly memorable dahlia border that begs a panoramic photo when you visit; similarly, Kelmarsh Hall in Northamptonshire has a dahlia collection to die for; and the National Dahlia Society is holding its own dahlia show at RHS Garden Wisley in September, complete with judging and demonstrations. Dave Gillam, Chair of the Society, has plenty of good advice on how to keep dahlias looking fabulous. “Generally the only thing dahlias don’t like is shade,” says Dave. “So, start by picking a sunny, open site. In winter, they can cope with cold and they can cope with wet, but not at the same time. So, if you have heavy soil but don’t want to lift them in autumn, the best bet is to create a slight mound at the bottom of their planting hole, so you’re raising the tuber above the natural water level. Add grit and plenty of organic matter when you plant, then in winter, simply cover the crown with straw as an organic mulch. “In garden situations, it’s worth trying to leave them in the ground over winter. If they survive that first year, when the plants are at their smallest, you’ll have them for life. It’ll save an awful lot of time and effort lifting and storing them. Besides, many dahlias are lost through improper winter storage – for instance, don’t put them in plastic bags or leave them in wet compost. “If you do decide to lift your tubers over winter, wake them up slowly in spring. Don’t plant them out until they’re showing actual signs of growth. Instead, plant the tubers in a pot on a warm windowsill and
If they survive that first winter you’ll have them for life
wait for them to show signs of life. Plant them out after the last frost and they’ll be in flower as early as June.” Dave has being growing dahlias since he was 10 and regularly competes in the National Championships against around 200 other serious exhibition growers. “My secret is to give the plants what they need before they need it,” he says. “If they’re showing signs of stress it’s too late. You have to keep the soil constantly moist, control the number of flowers and keep their stems well supported: I use three canes in an inverted pyramid to give the flowers plenty of room. “The hardest thing is getting them to flower at exactly the right time for exhibition. It’s a very concentrated effort – I grow about 460 dahlias on my allotment and I’m not allowed a hosepipe, so all the watering, as well as the weekly feeding, is done by watering can. But then, this is a Mexican plant that stores moisture in its tubers, so it can take pretty hot, dry conditions.” Over at Anglesey Abbey, Assistant Head Gardener David Jordan oversees the dazzling displays of 235 dahlias that bloom from mid-August into early autumn. Surprisingly, all of them are grown in three-litre pots and plunge-planted into the border in
June, when they’re showing a bit of bushy green top growth. “The tubers are planted in a mix of gritty compost we make ourselves, with added controlled-release fertiliser,” David explains. “In spring they start into growth and we start feeding them with a foliar feed. In late May, we’ll give them the ‘Chelsea chop’ to make them more bushy. Then we’ll take off all the first flowerbuds [see ‘stopping’ below] to divert their energy into growing tall. “In the second week of June we plunge the pots direct into the dahlia bed, about 5cm (2in) beneath the soil surface, to make a colour-coordinated display that’s different every year.” After the display has faded in autumn, the gardening team lifts all the dahlia pots to overwinter in a frost-free greenhouse, each pot clearly labelled and resting on its side. “We then dig in several tonnes of compost or leafmould into the border,” says David. “But all the effort is certainly worthwhile – visitors love our dahlias and come back year after year.”
You have to give the plants what they need before they need it