Williams has been growing potatoes this way for years and is now recommending Jamieson Brothers seed potatoes with growing instructions he has written himself.
He said: "It's a bit of fun and will give you the opportunity of harvesting new potatoes at Christmas." Williams added that gardeners should plant from early July to the third week in August.
Supplier JBA Seed Potatoes' Christmas potato collection is available from garden centres. Representative Iain Barbour said: "Christmas potatoes have been in huge demand with the general public over the past few years.
This year JBA is stocking Kestrel, Maris Peer, Carlingford, Charlotte, Pentland Javelin, Maris Bard and Nicola. It will also carry a few more unusual varieties, which will be available online only.