Posted: 03/07/2014 at 06:50
I left all my dahlias in the ground last winter and they have survived well. The only problem was that they are underplanted with daffs. and while the latter's foliage was dying down the whole bed became a mass of weed and dying foliage. Eventuallu I got in among it to clear it out and it is now fine. I have then mulched it with spent MPC... looks very neat. Other risk was slugs and snails chomping on the emerging dahlias down among the daffs/weeds, so had no choice but to broadcast pellets.
I used to store tubers and then pot them up as soon as buds started to show. They were stood outside in a sunny spot straight away, usually March/April ( if frost threatened I moved them overnight to shelter). So I grew them hard from the off, and I think this avoids legginess. A few dahlias which I grow in large pots, and which I am forcing to gain a head start for showing them at the local Show, are definitely taller but are strong and flowering well. Growing them on indoors seems to be the risk for legginess.
Hope this helps.