Beets are a root vegetable with both the root portion and the leaves being used for food. The young tender beet greens can be steamed, boiled or sauteed. Purchase beets with the greens still attached so you can tell the age of the beets as well as the greens. Purchase organic beets (for greens) whenever possible because the leaves are subjected to chemical spraying.
If you are harvesting your own beet greens you can start clipping them when they are about 9" high.
Roll up the greens lengthwise then cut them about 1/4" to 1/2" crosswise. You can boil or steam the greens, saute. To saute the greens, add the chopped greens to a saute pan with about 1 tablespoon olive oil (and a chopped garlic clove if you like garlic). Stir until the greens wilt. Add about 1/4 cup water, cover and steam until the greens are tender, about 10 minutes.