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Dahlias – the good, the better and the best!

In truth, not all that long ago, I thought of dahlias as a rather garish flower, usually seen at flower shows in the ‘Biggest Flower Head’ class. Then I met Darren who was growing them in bulk and bought a few and discovered that my rather small brain was missing a trick. Dahlias are the most generous and ingenious flower I have ever come across and I feel compelled to spread the word and make sure that everyone has at least one of these extraordinary bloomers in their garden – although I defy anyone to be able to choose “just the one”.

The dahlias in my flower patch started in mid-June and as I write at the end of October they are still blooming, although tainted by the hint of frost that has been teasing the early mornings. I have cut hundreds of stems for bouquets, parties, and weddings, and deadheaded even more. 

If you are keen to grow the best and most prolific dahlias then start with a good look at the soil. I grow on Kent clay which is full of nutrients, but well draining it isn’t and so I add large quantities of manure, leaf mould and green waste compost in winter and let the worms do their stuff through the season. Dahlias like a good draining soil but also like plenty of moisture so it is all about balance. When I plant my tubers after the first frosts in mid-May, I throw in some bonemeal and will then feed with a liquid low nitrogen feed every two weeks throughout the season. The better fed and hydrated your dahlias are, the more resistant they will be to pests and disease.

I always start my new tubers – or over-wintered stored ones – in pots in the polytunnel. The slug population loves nothing more than a delicious tender dahlia shoot which are like nectar to them so I leave it until they are well up and then plant with either some Strulch or sheep daggings around the base of the plant to discourage these slimy pests.

Once the shoots  are up to about 10” high, pinch out the central shoot by about 4” to above a pair of leaves. This will encourage branching and give you many more blooms.

Big, healthy dahlias need staking. I use a system with posts every 4 feet and then stock netting horizontally over them. I have it about 2 feet from the ground and this is enough to keep even the tallest dahlias straight and prevent breaking except in the most extreme weather. However if you only have a few dahlias, I would place a post in the ground before you plant your tuber and then tie in your main stem to the post.

Cutting dahlias at the optimal time to maximise vase life is an art! Too early and the dahlia won’t continue to open. Too late and the flower will have become papery and shatter. A real goldilocks dilemma. Look at the back of the flower head and you are aiming to find lush petals as the perfect stage. Give them a drink in lukewarm water to ensure best hydration or recut them under water.

If you are trying to keep them for a special occasion and need them to last as long as possible then cut the flowers directly into water, give them flower food and keep them as cool as possible.

Depending on whether you want dahlias to bring colour to your garden, for cut flowers or to win the biggest bloom at your local flower show will dictate which dahlias you should buy.

The ones I have found best for cutting are a mix of the ball, the pom pom, waterlily and semi-cactus Downham Royal, Peaches,Franz  Kafka, Gerrie Hoek, Arabian Night, Henriette, My Love, David Howard, Rosella and Rip City.

There are many, many varieties and colours to choose from so spend the winter months browsing the catalogues of companies like Peter Nyssen, Sarah Raven, Parkers or Withypitts, who are specialist growers in East Sussex.

Right now, the sword of Damocles in the shape of a sharp frost is hanging over the dahlias and the ones in the big bed need to be lifted to make space for spring bulbs. Until now I’ve always stored the tubers in compost in crates then covered the crates with a blanket, but since a visit to Pashley Manor gardens last summer and hearing the head gardener talk about how they store their dahlias I am going to give their way a try. He digs his tubers after the frost, cleans them off and once dry, stands them in open meshed crates sitting on their stalks with their tubers in the air. These crates are stacked one on top of the other and kept in the back of a frost-proof shed. This way he can check for rot easily as the tubers are not hidden. They have followed this way for many years and lost very few tubers. I’ll let you know in the spring how they fared. Having said that, the majority of my tubers stay in the ground over winter, covered with a good foot of compost and straw as a frost-defeating blanket, and if I didn’t need the room I would leave them all in.