Harvesting Potatoes

When is the right time to harvest potatoes? Also, why do some potatoes have a green tinge to them? Are they safe to eat if the green portion is removed?

Harvest potatoes once the tops have died. Get out the garden fork or spade to harvest the tubers (the part we eat) that develop 4 to 6 inches below the soil. Carefully dig the tubers using a garden fork or spade. Use any damaged potatoes immediately. Store only the unblemished tubers for later use. Avoid greening by protecting the developing and stored tubers from artificial light or sunlight. Plant potatoes at the proper depth, mound (hill) soil over the base of the plant and mulch with straw to keep light from reaching the tubers. Cover the potatoes in storage to prevent greening. You can still use the potatoes, just cut out the bitter tasting green parts.