Final update: the collection has been taken on my Louise Danks and moved to near Camborne. You can read about my visit to its new home here.
Update May 2021. The National Dahlia Collection has now relocated to Kehelland Trust near Cambourne in Cornwall. It is being managed by Louise Danks who has worked with the collection in the past. More information can be found on the Facebook page or Instagram
Update Sept 2020. The National Dahlia Collection has announced its closure. The reasons have not been given. Efforts are being made to relocate the collection.
In the middle of Cornish countryside within sniffing distance of the sea is what can only be described as dahlia heaven. From neat ball dahlias to the oversized, shaggy heads of giant decorative, and elegant anemone types, thousands of multi-coloured blooms fill a field. It’s a display that shows just how varied and beautiful these late summer flowers can be.
The National Collection is the perfect, if somewhat dangerous place, to choose varieties to grow – I ended with a long list for my cutting garden – yet it’s also just a lovely space to be in: peaceful and surrounded by flowers.
It’s been at its current site near Penzance since 1998, having been started in Oxfordshire in 1983 by David Brown. Today, it’s owned by Greenyard Flowers UK (formerly Winchester Growers), who have expanded the collection and brought it to the attention of the horticultural world with gold medal-winning displays at shows such as RHS Chelsea.
For a long time dahlias were out of fashion among gardeners and grown only by enthusiasts for competitions. In recent years, they’ve been rediscovered and are now a popular plant for late season colour.
“I think people have come to realise that they’re not just something that you grow in an allotment and put into a show,” says Mark Twyning, one of the team that looks after the dahlias.
It’s a wide-ranging collection with around 1,600 cultivars, although that’s a fraction of the number available worldwide, and 20 in the separate National Collection of species dahlias.
We had a slow walk around, slow because it was impossible to pass a plant without looking closer.
‘Sir Alf Ramsey’, is one of the best for the show bench, producing huge pink flowers. ‘Black Monarch’ has one of the darkest blooms, while ‘Wheels’ is a startling scarlet flower with a yellow collar of florets. Some, like the well-known ‘Bishop of Llandaff’ have the bonus of dark foliage.
One of the oldest in the collection is ‘Tommy Keith’, which dates from the 1890s, while the newer cultivars include the 20 Mark has raised, such as ‘Twynings After Eight’, ‘Chatsworth Splendour’ and ‘Carol Klein’.
Among Mark’s favourites is ‘Hamari Gold’: “Not only is the flower a lovely gold colour and just perfect, it also makes a nice sturdy plant.”
The collection is laid out in types – decorative, singles, waterlily etc. – with each plant labelled, and there’s a bed of seedlings that are being grown on to see if they produce something special.
Here and there are gaps in the rows, either waiting to be filled by new additions to the collection, or where rabbits, weather or virus have taken their toll. These plants will be replaced from cuttings taken from the ‘mother stock’, which is kept elsewhere on the farm.
‘The worrying thing is if we lose an old cultivar, unfortunately, the chances of finding it again are quite small.”
Mail order is now a big part of the National Collection and you can buy rooted cuttings and tubers of many of the dahlias, although some are not available while the numbers are bulked up.
Mark’s tips for growing dahlias
When it comes to growing, Mark says dahlias are unfussy over soil type but they do prefer a sunny spot.
Don’t plant them too deep and start tubers and cuttings off in pots in a warm spot, waiting until after the last frost before planting them out.
If you’re growing them in pots, they will need feeding and it’s also a good idea, if your soil is light and thin. Pot-grown plants will need fresh compost each season.
Slugs and snails can be a problem so guard your plants while they are young. Earwigs love hiding in dahlia flowers so, if you’re worried about them, Mark advises choosing single flowers – they are also loved by bees.
Keep deadheading to prolong the flowering and cut the plants down when the leaves are blackened by the first frost. In Cornwall, which is rarely bothered by extreme cold weather, Mark uses Bonfire Night as a good date.
If you’re on free-draining soil, you can leave tubers in the ground over winter. Just cover them well with a mulch of compost.
On heavy soil that holds water, or in very cold areas, it’s better to lift them and store them in a frost-free place.
The biggest problem is knowing what to choose and avoiding the commonly caught ‘dahlia addiction’.
Details about The National Dahlia Collection are on the website.
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Any update on its relocation?
It has been taken over but the new owner is being cagey about the location until they’ve got everything set up. It will have to be open to the public as a National Collection – part of the rules. When I find out more, I will post.