I've lived in Cornwall for the last 10 years, and it wasn't until last year that I found out that I've been driving past the National Dahlia collection virtually every day ! The collection is held down at Varfell Farm, near Penzance, and has a large field given over to the collection, with nearby sales of good sized plants, at a good price.
However this year a combination of a very cold winter and dry spring has meant that the annual open day has been cancelled, as the plants are a long way from their best. We had a walk round mid August, and it was a sorry sight. A lot of the labels had been damaged, flowers not opened, and plant sales not open. Nevertheless there were still an opportunity to photograph some of the varieties, and the on-line catalog is still of great interest if you're looking for an unusual plant.
In our own Cornwall Garden we have a variety of Dahlias, some in the garden, some in pots. In the past I've always dug Dahlia bulbs up and stored then, but I decided this year to leave them in the ground.. So when the really cold December hit us, and we had persistent snow and ice again ( unheard of going back 3 years ago), I put some straw and polythene over the ground where the plants were, and put the plants in pots into the shed. Come May they were coming up again, as right as rain, the only issue I had was that the badgers kept trying to dig the bulbs up, and they did damage one plant, other than that we had a good as display as last year.
To check out the on-line national dahlia collection click HERE Click on the first picture below to see a zoomed in slide show.