14" pots are a bit low, but you will get some potatoes. Once you've earthed up to the rim consider extending the height with cardboard or a ring of plastic from a compost bag. The higher you can go the better, but width is not so important. Just plant fewer tubers in each pot.
Potatoes need loads of water. But I've heard that you can earth up win straw, though I always use compost ( I know that will conserve the moisture). You can also feed them with a liquid manure or dilutes worm tea.