I've just dug up my first two potato plants. Started them very early (Feb) from the last eating potatoes of two supermarket bags - so, not 'proper' seed potatoes. Anyway, they looked very healthy as plants and I've just harvested 12 desiree and 10 white ones (maris piper / king edward, can't remember!). Nice size, some quite big.
Is that about right for yield or should I dig down some more? I found the original potato for both - does anything grow deeper than the 'mother spud'?