A herbaceous plant (Raphanus sativus) belonging to the mustard family (Cruciferae), the name radish is derived from Latin radix, root, no doubt because the radish is best known for its edible root. Radishes of the world are a variable lot: they may have red, black, purple, yellow, or white skins; they can be tiny or quite huge (over 2 feet long); round, oval, or elongated; but generally they have a pungent, peppery flavour. The leaves, particularly if young, are edible as well.
Radishes are thought to be descended from a plant native to China which spread to the Mediterranean thousands of years ago and made it to the new world by the 16th century. Roman poet Horace opined that they would excite the languid stomach, while Ben Jonson suggested eating them before tasting wine. Today, radishes are eaten throughout the world, particularly in China and Japan, where they are a staple, and often enjoyed after being pickled in brine.
Broadly speaking, radishes can be divided into two categories: spring and winter. Spring radishes are harvested young and are therefore usually smaller in size; among the spring radishes is the red globe radish familiar to most Europeans and North Americans, though there are many varieties of spring radish, including the surprisingly named French breakfast radish. Apparently the French are fond of dipping these in unsalted butter and munching them down with some crusty bread, which sounds odd but is apparently very delicious. Winter radishes are gathered later in the season; having longer to grow, they can become quite sizable. Daikon radishes are of this variety, though there are lots of other types besides.
Spring radishes are most often consumed, in my experience, sliced into salads or whole, with a dip. I'm not overly fond of them myself, and casting about for a way to use some leftovers from a party, I found a recipe for radishes sliced and sauteed in butter with shallots. Though this too sounded very odd, the sauteeing mellowed their flavour, and it was quite delicious. Thanks once again Joy of Cooking.
In spite of the similarity in names, horseradish, though cruciferous, is not in fact a radish.