Available in summer and plentiful in fall, Swiss chard is one of the healthiest of the super-nutritious "dark, leafy greens". It's never eaten raw, but should be cooked only briefly to make the most of its nutrients and mild flavor which resembles beet greens (which it technically is) or spinach. Chard requires little preparation as even the large stems can be eaten, but it should be washed well to get rid of all dirt and sand. Leaves should look vibrant and green and you should avoid any bunches that seem wilted or dried around the edges.