I put some of the Mira/Valor crosses that I grew from seed that Alan Romans sent me into 3 litre pots, as I was out of space elsewhere, dumped them in an old cold frame on the railway embankment, then ignored them apart from an occasional watering and 2 or 3 comfrey feeds. I emptied the first last night. Incredibly I got 1280g from the first pot. They were wedged so tight in the pot that it distorted the pot & malformed some of the spuds. They were gorgeous steamed as well.