Hi BA, really it does depend on the variety you go with. This year I had two lots (Maris Piper and Desiree) and found the former yielded around 10 pot's per plant while the later yielded less (around six - eight). Both varieties grew to around the same size so I would say the MP's yielded more weight than the Des.
I hope this helps a little.

Ian.

I grew Juliette as a salad potato and averaged 750g per root. My Desiree (main crop) got hit by blight so got lifted late August and averaged about 1.2kg per root. The Cara (main crop) were about 1.5kg per root, again they suffered to a degree from blight but not as badly as the Desiree. The original seed potatoes were from 3kg bags which gave my about 24 plants of Desiree and Cara and about 30 plants of the Juliette. This was my first year on the plot, on virgin ground and no manure added. They went in nearly a month later than the 'ideal' planting time so I would expect to add about 10% on to the above yield figures for next year (depending of course on weather).

Thanks, Ian and Rodger. I know it was a very vague question that could only receive a vague answere but this has all helped.

I think it's a very interesting one though BA and might make a good project for us this coming year, to gather the information and plot it out to see which varieties do better and which don't. I am planning to grow Ulster Prince this year as my dad (who was Noah's gardener!) claims they are the best!

Container gardening then, Ian?

I'm putting one of my new raised beds to potatoes to see how they get on BA. I have bought some of those collapsible container sack type things that I was going to use but don't think I will get enough in them so I'll use them for something else.