[HesterF]

So this is my first season of growing potatoes and I put all the types in at the end of March. They've all started coming through so I've been keeping them covered up with earth in case of frost. But now I'm hoping the last frost may have gone so how long do I continue to earth them up? Or at what point can I just let the tops grow? And how should I earth them up? Continue to add a little bit every time they stick their heads up or let them add a lot of top growth and then cover it all?

H

[Fleecewife]

By hoeing up the soil from around your plants you are not only protecting them from frosts but also the growing tubers from the light.  The tubers form above the original seed potato so you need a certain depth to cover them (how deeply they grow seems to vary with variety).  As you hoe, so you weed and this is one of the reasons potatoes are called a cleaning crop.  So carry on earthing up until there is no space between the plants.  You will then have a deep channel and a high ridge, the soil will be weeded then any further weeds shaded out.
 
Unless you are in a very mild area, last frost can happen up to the end of May, or even into June in some areas, so have fleece ready for when you can't earth up any more.