The radish (Raphanus raphanistrum subsp. sativus) is an edible root vegetable of the Brassicaceae family that was domesticated in Europe in pre-Roman times. Radishes are grown and consumed throughout the world, being mostly eaten raw as a crunchy salad vegetable. They have numerous varieties, varying in size, flavor, color, and length of time they take to mature. Radishes owe their sharp flavor to the various chemical compounds produced by the plants, including glucosinolate, myrosinase, and isothiocyanate. They are sometimes grown as companion plants and suffer from few pests and diseases. They germinate quickly and grow rapidly, smaller varieties being ready for consumption within a month, while larger daikon varieties take several months. Another use of radish is as cover or catch crop in winter or as a forage crop. Some radishes are grown for their seeds; daikon, for instance, may be grown for oil production. Others are used for sprouting and both roots and leaves are sometimes served cooked or cold.
Varieties of radish are now broadly distributed around the world, but almost no archeological records are available to help determine their early history and domestication. However, scientists tentatively locate the origin of Raphanus sativus in southeast Asia, as this is the only region where truly wild forms have been discovered. India, central China, and central Asia appear to have been secondary centers where differing forms were developed. Radishes enter the historical record in third century BC. Greek and Roman agriculturalists of the first century AD gave details of small, large, round, long, mild, and sharp varieties. The radish seems to have been one of the first European crops introduced to the Americas. A German botanist reported radishes of 100 lb (45 kg) and roughly 3 ft in length in 1544, although the only variety of that size today is the Japanese Sakurajima radish. The large, mild, and white East Asian form was developed in China, but is mostly associated in the West with the Japanese daikon, owing to Japanese agricultural development and larger exports.
Radishes are annual or biennial brassicaceous crops grown for their swollen tap roots which can be globular, tapering, or cylindrical. The root skin colour ranges from white through pink, red, purple, yellow, and green to black, but the flesh is usually white. Smaller types have a few leaves about 13 cm (5 in) long with round roots up to 2.5 cm (1 in) in diameter or more slender, long roots up to 7 cm (3 in) long. Both of these are normally eaten raw in salads. A longer root form, including oriental radishes, daikon or mooli, and winter radishes, grows up to 60 cm (24 in) long with foliage about 60 cm (24 in) high with a spread of 45 cm (18 in). The flesh of radishes harvested timely is crisp and sweet, but becomes bitter and tough if the vegetable is left in the ground too long. Leaves are arranged in a rosette. They have a lyrate shape, meaning they are divided pinnately with an enlarged terminal lobe and smaller lateral lobes. The white flowers are borne on a racemose inflorescence. The fruits are small pods which can be eaten when young.
The radish is a diploid species, and has 18 chromosomes (2n=18).