The whole reason for the selfsufficientish website was to offer a place where anyone can ask, HOW DO I...? So who knows why it has taken us so long to have a HOW DO I? section, but here it is. So if you want to know how to do anything selfsufficientish then here is the place to ask.
A lot depends one where you live and how deep you planted them, also whether they are earlies or maincrop, but I would say that they are probably just about to break through the surface as we speak. One thing is pretty certain, potatoes will grow whatever you do to them, so I wouldn't worry too much.
I planted some second earlies on the 20th of March and some are just poking through now.
Tony
Disclaimer: I almost certainly haven't a clue what I'm talking about.