Radish

• 1. Introduction

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  A German botanist in 1544 claimed to have seen radishes weighing 100 pounds and stretching roughly 3 feet long. That report sounds like a tall tale. Yet the radish, a flowering plant in the mustard family Brassicaceae, really does range from tiny salad globes to monsters of the soil. Its large taproot is the part most people eat, though the entire plant is edible, leaves and all. It was domesticated first in Asia, and now it grows almost everywhere. How does one humble root vegetable hold a black-skinned winter form, a 30-kilogram Japanese giant, and a tradition of carving it into religious figures? The answers lie in its chemistry, its varieties, and the cultures that have prized it.

• 2. The Chemistry Of Heat

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  Glucosinolate, myrosinase, and isothiocyanate are the compounds behind a radish's sharp bite. When the raw flesh is chewed, glucosinolates and the enzyme myrosinase combine to form allyl isothiocyanates. That same family of compounds gives mustard, horseradish, and wasabi their pungency. The intensity is not fixed. A radish's peppery flavor varies depending on its growing environment, and homegrown specimens can be significantly sharper than store-bought ones. Color comes from a different set of chemicals. Roots draw their hues from anthocyanins, with red varieties using pelargonidin as a pigment and purple cultivars taking their color from cyanidin. Beneath that skin, the flesh is usually white. Even the timing of harvest changes the experience. Pulled at the proper time a radish is crisp and mild, but left in the ground too long it turns bitter and tough.

• 3. A Spectrum Of Forms

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  Skin color in radishes runs from white through pink, red, purple, yellow, and green all the way to black. Shapes are just as varied: globular, tapering, or cylindrical taproots, some growing longer than a parsnip. Smaller types carry a few leaves about 13 centimeters long above round roots up to 2.5 centimeters across, or slender roots up to 7 centimeters. A longer form, which includes oriental radishes, daikon or mooli, and winter radishes, can reach 60 centimeters in length with foliage about 60 centimeters high and a spread of 45 centimeters. The leaves grow in a rosette and take a lyrate shape, divided pinnately with an enlarged terminal lobe and smaller lateral lobes. White flowers sit on a racemose inflorescence, followed by small pods that can be eaten when young. At the cellular level the radish is a diploid species with 18 chromosomes, and its genome is estimated to contain between 526 and 574 megabases.

• 4. Tracing The Roots

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  Almost no archeological records exist to chart the radish's early history and domestication. Scientists have tentatively placed the origin of Raphanus sativus in Southeast Asia, the only region where truly wild forms have been found. India, central China, and Central Asia appear to have been secondary centers where different forms developed. Radishes enter the historical record in the third century BC. By the first century AD, Greek and Roman agriculturalists were describing small, large, round, long, mild, and sharp varieties. The plant traveled fast once Europeans crossed the Atlantic, becoming one of the first European crops introduced to the Americas. The large, mild, white East Asian form was developed in China, yet in the West it is mostly associated with the Japanese daikon, a result of Japanese agricultural development and larger exports.

• 5. Quick To Grow

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  Three to four days is all radish seed needs to germinate in moist soil between 65 and 85 degrees Fahrenheit. Under average conditions the crop matures in three to four weeks, though colder weather can stretch that to six or seven. Best-quality roots come from moderate day lengths with air temperatures of 50 to 65 degrees Fahrenheit. The plant favors full sun in light, sandy loams with a soil pH of 6.5 to 7.0, while a clayey-loam suits late-season crops. Soils that bake into a crust impair germination. Planting depth even shapes the root, from 1 centimeter for small radishes to 4 centimeters for large ones. This speed and ease make radishes a frequent choice for novice gardeners, and the fast harvest cycle makes them particularly suitable for children's gardens. After harvest the roots keep two or three days at room temperature, or about two months at 0 degrees Celsius with relative humidity of 90 to 95 percent.

• 6. Allies And Enemies

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  A radish's pungent odour does work in the garden beyond the plate. Grown as companion plants, radishes deter insect pests such as aphids, cucumber beetles, tomato hornworms, squash bugs, and ants. They can also act as a trap crop, luring pests away from a main crop. Cucumbers and radishes thrive in close association, and radishes also pair well with chervil, lettuce, peas, and nasturtiums, though they react badly to hyssop. They are not invincible. The adult flea beetle bites small shot holes in leaves, especially of seedlings, while its larvae live in the soil. The swede midge, Contarinia nasturtii, attacks foliage and growing tips, causing distortion, multiple or absent growing tips, and swollen or crinkled leaves and stems. The cabbage root fly's larvae sometimes attack the roots, where small white maggots tunnel through and leave the flesh inedible.

• 7. Named Cultivars

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  'Cherry Belle', a bright red-skinned round radish with a white interior, is familiar in North American supermarkets. It shares the spotlight with a long roster of named varieties. 'White Icicle' is a white carrot-shaped type around 10 to 12 centimeters long, dating back to the 16th century. 'Bunny Tail' is an Italian heirloom known there as Rosso Tondo A Piccola Punta Bianca, slightly oblong and mostly red with a white tip. 'French Breakfast' carries a white splash at its root end and is among the quickest to turn pithy. 'Easter Egg' is not a true variety at all but a mix sold under one name, blending white, pink, red, and purple radishes to spread out the harvest. Winter forms run heavier. 'Black Spanish', dated in Europe to 1548 and known in French as Gros Noir d'Hiver, has rough black skin over hot white flesh and grows to around 10 centimeters across. The Sakurajima radish is typically grown to around 10 kilograms but can reach 30 kilograms if left in the ground.

• 8. Seeds Toys And Festivals

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  Wild radish seeds contain up to 48 percent oil, unfit for human consumption but a potential source of biofuel. Some radishes are grown not for roots but for their seeds, which grow in siliques widely called pods. The rat-tailed radish, an old European variety thought to trace back to East Asia, produces long, thin, curly pods that can exceed 20 centimeters, and in the 17th century those pods were often pickled and served with meat. The plant also reaches deep into culture. Asaph the Jew noted the radish, especially its leaves, in traditional medicine to increase mucus, Ibn Wahshiyya treated it as part of poison antidotes, and Maimonides highlighted its possible uses as a treatment. In Japan and Korea, radish dolls are sometimes made as children's toys, and daikon appears in the Japanese Festival of Seven Herbs on the seventh day after the new year. Each December 23, the citizens of Oaxaca, Mexico, hold the Night of the Radishes, carving a large type up to 50 centimeters long and 3 kilograms into religious and popular figures displayed in the town square.