High in fiber, full of iron, and loaded with cancer-fighting beta-carotene and folic acid, beets are powerhouse vegetables. Even more nutritious than the bulbous root? The greens on top, which taste like Swiss chard and can be similarly prepared. Beets will last a month in the refrigerator, but the greens need to be used within a few days. Get our Sauteed Beet Greens recipe.