To me, their most appealing trait of all is how easy they are to grow. For years, I cast jealous glances at the dahlia bed of my allotment neighbour. The lavish blooms of riotous colour seemed too impressive to be achievable. How wrong I was! Last year, I finally summoned the courage to have a go myself and for months I was the smug bearer of huge bouquets of flowers.
HOW TO GROW THEM
In March or early April, start your dahlias off in pots, be they rooted cuttings or tubers. If you are using tubers that have been in storage over winter, give them a thorough inspection and cut off any diseased or soggy pieces with a clean knife. If you are planting a tuber, look for last year's stems and plant with these to the top. If you are using rooted cuttings, gradually pot on, increasing the size of pot as your plant grows.
Keep the pots well watered and when your dahlias reach about 40cm tall, pinch out their growing tips just above a set of leaves. This will encourage them to bush out.
After the last frost has past, plant out your dahlias in the garden. Always stake your dahlias as soon as you plant them out and then tie them in as they grow. When the plants are fully established, they will hide any unsightly sticks and won't slump over. Use strong pieces of wood, not bamboo, which is the perfect hiding place for earwigs who will snack on your tender plants. Always protect against slugs - this is particularly important in the early stages to avoid heartbreak.
As soon as you see buds developing, start feeding your dahlias. The folks at the National Dahlia Collection recommend a proprietary tomato food once every 10 days.
When your plants start blooming, be meticulous about deadheading. If you keep on picking the flowers, you'll have a constant supply of blooms from July to November. Before you put them in a vase, Sarah Raven recommends re-cutting the hollow stem under water to avoid airlocks.
There is some controversy about whether to dig up your dahlias each winter. If you have space to store your tubers in a cool, dry place and live somewhere where you are likely to get waterlogged soil and quite a few frosts come winter, it is well worth putting the effort in.
The National Dahlia Collection sell rooted cuttings, most of which will flower in their first year and also establish a tuber. If you are growing dahlias from cuttings it is recommended that you leave them in the ground for as long as possible as the majority of weight is put on tubers towards the end of the growing season. An easy way of timing this is to let your dahlias take the first frost of winter - following this, their leaves will go brown and they will look generally sorry for themselves. At this point, carefully dig them up, cut back the growing stems and then leave them to dry upside-down, so that any damp left in the stems can drain out.
Once the tubers are nice and dry, put them away for winter. Damp is the enemy here. I follow the lead of my allotment mentors and use plastic fruit boxes with holes to all four sides and base. You want your tubers to be fully ventilated but if they are in an unheated shed, it's a good idea to cover them with some newspaper to prevent damp and frost from settling on them.
Where to buy them
The National Dahlia Collection sell their astonishing collection of rooted cuttings by mail order until the end of March. They grow over 1,600 varieties in their 2-acre garden in Penzance which is open to the public from mid-July to the end of September. This year they will be exhibiting at both Chelsea and Hampton Court Flower Shows.
Sarah Raven is a figurehead for the dahlia's triumphant return to fashion. She grows a huge number of dahlias in her garden at Perch Hill and sells tubers via her website. This year she is holding a dahlia celebration day in September when the plants will be at their floriferous best. Visitors will be shown around both Perch Hill and Great Dixter and Sarah and the team at Dixter will explain how to choose the most beautiful and productive plants. Buy tickets here
de Jager was established in Holland in 1868 as flower bulb specialist. It maintains its reputation for producing the highest quality bulbs and in 2012 was granted a Royal Warrant as supplier of garden flower bulbs to The Prince of Wales. It sells an excellent range of dahlia tubers, including dinner plate dahlias for show.
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Original article and pictures take http://www.houseandgarden.co.uk/outdoor-spaces/features/dahlia-mania site