Radishes are crisp and crunchy with a pungent, peppery flavor. There are varying degrees of "spiciness" based on when they're grown, as well as actual size of the radish. Larger radishes are typically spicier, and radishes grown in hotter temperatures are normally spicier as well. The interesting part about the taste of radishes is that they're not peppery until you bite into them. The peppery flavor is caused by glucosinolates and an enzyme called mirosinase, which are combined during the chewing process. Chewing forms allyl isothiocyanates, which is also present in horseradish and wasabi. Hey, I learned something new here!