[rikknikk]

Can I just check that you only need to earth up potatoes if a frost is expected?

[Troopersnoots]

Yes and no, we earth them up in early spring to protect from frost, the main purpose for earthing up is to create room for your little tatties to grow into.

[DD.]

The main reason is to exclude light, if you don't earth up, the spuds will grow at the surface and go green. This is toxic, (not fatal, but could give you a bad stomach).

[solway cropper]

Some people don't earth up but as DD says you need to protect the tubers from light. You could mulch around them or use cardboard/straw, anything to exclude light.