A scape is a stalk that rises from a root under the earth. Hardneck garlic has a flower stalk the ascends through the leafy portion of the plant and then twists into a curl or coil; it's topped by a capsule called an umbel. If left to develop naturally, the garlic will throw all its energy into the flower. But if the scape is harvested before the flower develops, it makes a tasty vegetable and an attractive garnish. Garlic scapes are also known as green garlic or garlic spears.
Garlic scapes are harvested in late spring. You can chop them up and use them as you would garlic; the taste is similar, though very mild. You can also saute them in olive oil or garlic and serve them as an accompaniment to a meat main course, seasoned with a little salt and pepper. Or you can blanch or grill them and serve them the same way. They're great chopped up and added to mashed potatoes, and they make an excellent pesto.
Buy scapes that are fresh and bright green. They keep for weeks in a paper bag in the fridge.
sneff, bless his heart, has a pretty mean looking garlic scape frittata recipe over at green garlic. (Gotta love a man that cooks, especially one who cooks like that!)
Cletus the Foetus says: "I think garlic is actually named for its scapes. 'Garlic' from Old English garlic (pronounced 'gar-lich'), 'spear-like.'" (I say: Love those brainy boys!)