Sorry guys ..bumping this very old thread ...
I'm trying to grow sweet potatoes in bags on a very warm bit of patio this year. I bought (from ebay) two colder climate tubers in order to make my own slips.
I've had the tubers in a jar of water for the last couple of weeks .. I've had them on top of the central heating boiler .. so far so good. Both tubers have thrown up shoots and yesterday I broke off some of the longer ones and put them in another jar of water and they have already sprouted roots that, in the last 24 hours, have grown over a centimetre ! They are, apparently, a bit of a thug if they are in the ground and get out of hand.
Once the roots have established I'll get them into pots and then, subequently, into the potato bags ...
There are lots of tales of people having tried and failed in the UK so I'm only trying them as an experiment as my family like sweet potatoes ... So, watch this space ...