Radishes are root vegetables with a distinctive flavour that range from the juicy crispness of the familiar red globe radish to the sharp bite of the turnip shaped black radish. Like their relatives broccoli, cabbage, and kale, radishes are cruciferous vegetables that offer cancer protecting potential. They were first cultivated thousands of years ago in China, then in Egypt and Greece (where the vegetable was so highly regarded that gold replicas were made of it). Since then, many varieties have been developed in a number of shapes, sizes, and colours.
In the UK , radishes are usually eaten raw; however, they can be added to cooked dishes such as soups, or pickled, or heated and served as a whole vegetable when they lose their spicy taste, but are delicious. As with many other root vegetables, their green tops are edible and lend a peppery taste to salads. While radishes are not nutritionally outstanding, they are a good source of vitamin C. They make a perfect, very low calorie snack food. Growers classify radishes by shape,round, oval, oblong, and long are the most common. Markets frequently label them by colour, red, white, and black ones are the most frequently available. Black radishes are turnip like in size and shape (about 8" long), these have dull black or dark brown skin. When peeled, their flesh is white, quite pungent, and drier than other radishes. "Black Spanish" is the name for commercially grown black radishes, which are available in round and long varieties.
Although red globe radishes can grow to 4" or 5" in diameter, the ones in the produce department will probably be closer to the size of a ping-pong ball, about 1" to 1 1/2" in diameter. Much larger than that, red radishes are likely to be woody.
Radishes with their leaves intact are usually tied in bunches, while topped radishes are sold in plastic bags. If the leaves are attached, they should be crisp and green. Look for well-shaped radishes with good colour. Whether red or white, the roots should be hard and solid, with a smooth, unblemished surface. Check bagged radishes to make sure they are free of mould.
Black radishes should be solid, heavy, and free of cracks. Daikons, which may be found at Asian markets and many supermarkets, should be evenly shaped and firm, with a glossy, almost translucent sheen.
If you've bought radishes with their leaves attached, remove the tops unless you'll be serving them the same day (leaf-topped radishes are handsome on a crudite platter). Radishes will not keep as well with their tops left on. The leaves, if fresh and green, can be cooked like other greens or used in soups. Place radishes in plastic bags if they are not already packaged. Both red radishes and daikons will keep for up to two weeks in the refrigerator. Black radishes can be stored for months if they remain dry; store them in perforated plastic bags in the refrigerator.
Scrub the radishes and trim off the stem end and tip. Since it is their skin that contains most of the enzymes that form the mustard oils responsible for their pungency, you may want to peel the radishes. However, red globe and white icicle radishes are rarely hot enough to warrant paring (and it's a shame to remove the globes' cherry red skin). Daikons have a very thin skin that can be removed with a vegetable peeler, if you wish. Black radishes should be well scrubbed; whether you peel them or not depends on the thickness of the skin. If it is thin, leave it on; the dark color provides a striking contrast with the white flesh.
Small radishes can be served whole, raw, or cooked; black radishes and daikons, which are larger and sharper, are usually cut up or grated.