Posted: 16/05/2015 at 17:16
They will flower when they are ready. Not all potatoes flower. Maybe you misunderstand why you are earthing up. It is not to stop the plant flowering.
It is to make sure the developing potatoes are covered up and to warm up the soil, because the sun shines on the sloping sides.
When you think they might be ready, dig gently around in the soil with your hand and see if you find potatoes of usable size. You can gently pick those off the roots and cover up the rest to go on growing.