Posted: 16/05/2012 at 13:59
i always "earth up" potatos till there is ruffly (sometimes less) a foot of soil on top, i do this gradually so the leaves keep coming up. After this you leave the leaves to grow and make like a bush on top, they will then flower and after this die back a bit which is when you dig them up (you can dig before but i find if you wait you get more spuds).
Earthing up helps the plant produce more spuds as there is more room.
Hope this helps im only a novice and i know how puzzling it can be.