You plant the whole thing (the tentacles use the spud for energy until they grow leaves). You can even cut each potato into pieces, although you should make sure each piece has at least 3 eyes.

Potatoes, like most vegetables, will take all the sun you can give them. But don't let a little shade prevent you from planting them; potatoes are pretty easy to grow. Like most roots, you want to plant them in loose soil (if nothing else, it makes digging them out at the end a lot easier). If you want to get fancier, once they start producing foliage, you can add more loose dirt over them (leaving some of the foliage uncovered); sometimes they will then produce more spuds.

One final thing: your potatoes may flower and produce tomato-like fruit. Don't eat it. It's poison. You can save the seed from the fruit to try to get true potato seed (as opposed to re-using the sprouting spuds, which causes disease problems after a few generations).

Territorial Seed (www.territorialseed.com) is a good source for general info about planting vegetables around here. They say:

"CULTURE: Potatoes grown in loose, well-drained soil produce the best yield. Up to 3 weeks before your last frost date, plant seed potatoes 4-6 inches deep, 12 inches apart, in rows 12-24 inches apart. Larger potatoes can be cut to use as seed. Be sure to leave at least 3 eyes per piece. If soils are heavy, plant 2-3 inches deep and cover with 2-3 inches of mulch. Irrigate heavily when needed, and allow the soil to dry out somewhat before watering again. Mulching will help prevent sunscald. Apply a fertilizer that is low in nitrogen and high in phosphorus. Bone meal is a good choice. Use 5-7 pounds per 100 square feet.

HARVEST: Many varieties die-down on their own to let you know they are ready to harvest. If the plants are still growing and your potatoes have reached that perfect size, you can stop growth by breaking or cutting off the plant foliage. Potatoes should be left in the ground for about 2 weeks after vines have died or have been cut down. This allows the skins to set and increases storage ability. Standard potatoes yield about 10 times the amount originally planted. Fingerling potatoes yield from 15 to 20 times the amount originally planted.

STORAGE: Store potatoes in a relatively dry location and at the lowest temperature possible without freezing."

Note: last frost date in Seattle is April 15, so 3 weeks prior is March 25. Keep your potatoes in a cool, dry place until then.