Posted: 16/03/2014 at 15:21
Mel, the main reason for earthing up is to make sure the potatoes are covered so they don't go green if they are exposed to the light.
When they are in a garden it also allows the sun to warm up the potatoes when it shines on the sides of the earthing-up. It also directs the rain water down to the roots/potatoes.
Although it does work, it is not the best idea to grow potatoes from sprouting potatoes you bought from the supermarket. They may carry all sorts of nasties which may show themselves if they do not have a regular dose of pesticide or herbicide which amateur gardeners would not want to apply..
As a rough guide, you will have usable potatoes when the plant flowers. Though not every variety does flower.
Conquer your dislike of spiders (you really are bigger than them) and get the plants out into good light as soon as you can, but make sure they do not get frosted.
Cover them with a sheet of newspaper overnight if frost is threatened.