Radish

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, colour 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.

History

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.

Cultivation

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.

Varieties

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.

Spring or summer radishes

Sometimes referred to as European radishes, or as spring radishes if they're typically planted in cooler weather, summer radishes are generally small and have a relatively short 3-4 week cultivation time.

• The April Cross is a giant white radish hybrid that bolts very slowly.
• Cherry Belle is a bright red-skinned round variety with a white interior. It is familiar in North American supermarkets.
• Champion is round and red-skinned like the Cherry Belle, but with slightly larger roots, up to about 5 cm, and a milder flavor.
• Red King has a mild flavor, with good resistance to club foot, a problem that can arise from poor drainage.
• Snow Belle is an all-white variety of radish, also round like the Cherry Belle.
• White Icicle or just Icicle is a white carrot-shaped variety, around 10-12 cm long, dating back to the 16th century. It slices easily, and has better than average resistance to pithiness.
• French Breakfast is an elongated red-skinned radish with a white splash at the root end. It is typically slightly milder than other summer varieties, but is among the quickest to turn pithy.
• Plum Purple a purple- fuchsia radish that tends to stay crisp longer than the average radish.
• Gala and Roodbol are two varieties popular in the Netherlands in a breakfast dish, thinly sliced on buttered bread.
• Easter Egg is not an actual variety, but a mix of varieties with different skin colors, typically including white, pink, red, and purple radishes. Sold in markets or seed packets under the name, the seed mixes can extend harvesting duration from a single planting, as different varieties may mature at different times.

Winter varieties

Black Spanish or Black Spanish Round are occur in both round and elongated forms, and is sometimes simply called the black radish or known by the French Gros Noir d'Hiver. It dates in Europe to 1548, and was a common garden variety in England and France the early 19th century. It has a rough black skin with hot-flavored white flesh, is round or irregularly pear shaped, and grows to around 10cm in diameter.

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.

Seed pod varieties

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.

Nutritional value

Radish, raw, root only

Nutritional value per 100 g (3.5 oz)
Energy	66 kJ (16 kcal)
Carbohydrates	3.40 g
- Sugars	1.86 g
- Dietary fibre	1.6 g
Fat	0.10 g
Protein	0.68 g
Thiamine (vit. B1)	0.012 mg (1%)
Riboflavin (vit. B2)	0.039 mg (3%)
Niacin (vit. B3)	0.254 mg (2%)
Pantothenic acid (B5)	0.165 mg (3%)
Vitamin B6	0.071 mg (5%)
Folate (vit. B9)	25 μg (6%)
Vitamin C	14.8 mg (18%)
Calcium	25 mg (3%)
Iron	0.34 mg (3%)
Magnesium	10 mg (3%)
Phosphorus	20 mg (3%)
Potassium	233 mg (5%)
Zinc	0.28 mg (3%)
Percentages are relative to US recommendations for adults. Source: USDA Nutrient Database

Radishes are rich in ascorbic acid, folic acid, and potassium. They are a good source of vitamin B6, riboflavin, magnesium, copper, and calcium. One cup of sliced red radish bulbs provides approximately 20 Calories or less, coming largely from carbohydrates, making radishes, relative to their size, a very filling food for their caloric value.

Uses

In cooking

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.

In medicine

Radishes are suggested as an alternative treatment for a variety of ailments including whooping cough, cancer, coughs, gastric discomfort, liver problems, constipation, dyspepsia, gallbladder problems, arthritis, gallstones, kidney stones and intestinal parasites.

In industry

The seeds of the Raphanus sativus species can be pressed to extract seed oil. Wild radish seeds contain up to 48% oil content, and while not suitable for human consumption the oil has promise as a source of biofuel. The oilseed radish grows well in cool climates.

Radishes in popular culture

• Radishes were a favourite food of Fraggles, Gorgs and Doozers in the children's television program Fraggle Rock
• Homestar Runner's Reddest Radish