Or be a radish purist and crunch on them at will. They make a great low-calorie snack. You can purchase radishes with or without leaves. If you buy them leaf-on, remove the leaves before storing. The leaves tend to hoard some of the moisture.
Radishes are mostly water, so they like to stay moist and cool in the refrigerator.
If you want to maximize your radishes' shelf life, store them in a perforated plastic bag in the refrigerator. Don't wash them until you are ready to use them. If you want to go beyond red, you can find sea-green daikon radishes. Daikons are long with a white interior and can range from mild to very spicy. You can peel and slice daikon very thin and toss it in salads, or cube it or cut it into sticks to munch on.