Posted: 17/11/2014 at 14:32
Thanks for the advice everyone. I already have a small plastic one which gets quite full at times which is why ive spilled over into the shed slightly. I never thought that i would enjoy gardening as much as i do and didnt realise the amount of tools needed for the job!
You've nearly answered your own question Vic!
In short, no you don't need a greenhouse to overwinter dahlias - just somewhere frost free. BUT - if you have found that you really enjoy gardening & are starting to struggle for space in a mini greenhouse and starting to use the shed as one - well I can only think that a proper full size greenhouse will increase your enjoyment many times over.
It is, however, a fairly major purchase - especially if you start putting down a decent base, installing electricity and buying lots of accessories. It is worth doing a lot of homework to find the right size & construction for your needs & pocket as well as working out the best site for access & sun etc. Lots of free advice available from the forum as you know & we're all getting a bit bored now winter is approaching so plenty of time to share our experiences!!
As a first off from me - I would say go for the biggest one you can accommodate without spoiling the look of your garden, consider installing electric so you can operate propagators & thermo controlled heaters and try to get a water supply next to it or nearby so you are not walking miles to water plants (a filled water butt is fine - doesn't need to be mains). Also make sure you can walk round the outside to clean or possibly repair it.
PS - We've all made loads of mistake along the way - that's why we don't laugh at anybody else's