Potatoes in containers - why OK to put closer together than in open ground?

[JamonSerrano]

Hello. Can anyone explain to me why you are advised to plant potatoes in the ground at - give or take - a foot apart, yet at the same time it's considered OK to put them a matter of inches apart in bags / pots? Is it just that the yield is very much reduced in containers? Companies selling potato growers always seem to imply that you get a bumper crop...

[DavidT]

In containers you get a lot of smaller "new" potatoes. In the ground they, obviously, grow bigger.