The radish (Raphanus sativus) is an edible root vegetable of the Brassicaceae family that was domesticated in Europe in pre-Roman times. They are grown and consumed throughout the world. Radishes have numerous varieties, varying in size, color and duration of required cultivation time. There are some radishes that are grown for their seeds; oilseed radishes are grown, as the name implies, for oil production.
Although the radish was a well-established crop in Hellenistic and Roman times, which leads to the assumption that it was brought into cultivation at an earlier time, Zohary and Hopf note that "there are almost no archeological records available" to help determine its earlier history and domestication. Wild forms of the radish and its relatives the mustards and turnip can be found over west Asia and Europe, suggesting that their domestication took place somewhere in that area. However Zohary and Hopf conclude, "Suggestions as to the origins of these plants are necessarily based on linguistic considerations.
The descriptive Greek name of the genus Raphanus means "quickly appearing" and refers to the rapid germination of these plants. Raphanistrum from the same Greek root is an old name once used for this genus.
Summer radishes mature rapidly, with many varieties germinating in 3-7 days, and reaching maturity in three to four weeks. A common garden crop in the U.S., the fast harvest cycle makes them a popular choice for children's gardens. Harvesting periods can be extended through repeated plantings, spaced a week or two apart.
Radishes grow best in full sun and light, sandy loams with pH 6.5 - 7.0. They are in season from April to June and from October to January in most parts of North America; in Europe and Japan they are available year-round due to the plurality of varieties grown. As with other root crops, tilling the soil helps the roots grow. Most soil types will work, though sandy loams are particularly good for winter and spring crops, while soils that form a hard crust can impair growth. The depth at which seeds are planted affects the size of the root, from 1 cm deep recommended for small radishes to 4 cm for large radishes.
Broadly speaking, radishes can be categorized into four main types (summer, fall, winter, and spring) and a variety of shapes, colours, and sizes, such as black or multi-coloured radishes, with round or elongated roots that can grow longer than a parsnip.
Daikon refers to a wide variety of winter radishes from east Asia. While the Japanese name daikon has been adopted in English, it is also sometimes called the Japanese radish, Chinese radish, or Oriental radish. In areas with a large South Asian population, it is marketed as mooli. Daikon commonly have elongated white roots, although many varieties of daikon exist. One well known variety is April Cross, with smooth white roots. The New York Times describes Masato Red and Masato Green varieties as extremely long, well suited for fall planting and winter storage. The Sakurajima daikon is a hot flavored variety which is typically grown to around 10 kg when harvested, but which has grown as heavy as 30 kg when left in the ground.
The seeds of radishes grow in pods, following flowering that happens when left to grow past their normal harvesting period. The seeds are edible, and are sometimes used as a crunchy, spicy addition to salads. Some varieties are grown specifically for their seeds or seed pods, rather than their roots. The Rat-tailed radish, an old European variety thought to have come from East Asia centuries ago, has long, thin, curly pods which can exceed 20cm in length. In the 17th century, the pods were often pickled and served with meat. The München Bier variety supplies spicy seeds that are sometimes served raw as an accompaniment to beer in Germany.
The most popular part for eating is the napiform taproot, although the entire plant is edible and the tops can be used as a leaf vegetable. The skin comes in a variety of colours. Most commonly known is the round, red-skinned variety but other varieties may have a pink, white or gray-black skin, and there is a yellow-skinned variety.
The bulb of the radish is usually eaten raw, but tougher specimens can be steamed. The raw flesh has a crisp texture and a pungent, peppery flavor, caused by chewing glucosinolates and the enzyme myrosinase in the radish, that, when brought together form allyl isothiocyanates , also present in mustard, horseradish and wasabi.
Radishes can be used in salads, as well as in many European dishes.