"When the shoots reach 20cm tall, use a rake, hoe or spade to mound soil up around the bases of the shoots, covering the stems half way. This is called earthing up."
"Water potatoes regularly, especially during warm, dry spells, and keep the soil weed free. As the potato plants grow, use a spade or hoe to cover the shoots with soil to stop the developing tubers becoming green and inedible. This is called ‘earthing up’. Leave the top few centimetres poking out the top. As plants continue to grow you will need to earth them up again."