About Raphanus sativus L.
Raphanus sativus L., commonly known as radish, is an annual or biennial brassicaceous crop grown for its swollen tap roots, which can be globular, tapering, or cylindrical. The skin color of the root ranges from white through pink, red, purple, yellow, and green to black, while the flesh is usually white. Roots get their color from anthocyanins: red varieties use the anthocyanin pelargonidin as a pigment, and purple cultivars get their color from cyanidin. Smaller radish types grow a few leaves around 13 centimeters (5 inches) 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 smaller types are normally eaten raw in salads. Longer root forms, including oriental radishes, daikon or mooli, and winter radishes, can grow up to 60 cm (24 in) long, with foliage around 60 cm (24 in) high and a spread of 45 cm (18 in). When harvested timely, radish flesh is crisp and sweet, but becomes bitter and tough if the vegetable is left in the ground too long. Radish leaves are arranged in a rosette, and have a lyrate shape, meaning they are divided pinnately with an enlarged terminal lobe and smaller lateral lobes. White flowers grow on a racemose inflorescence, and the fruits are small pods that can be eaten when young. Radish is a diploid species with 18 chromosomes (2n=18), and its genome is estimated to contain between 526 and 574 Mb. Radishes are a fast-growing, annual, cool-season crop. Their seeds germinate in three to four days in moist conditions, when soil temperatures are between 18 and 29 °C (65 and 85 °F). The best quality roots grow under moderate day lengths, with air temperatures in the range of 10 to 18 °C (50 to 65 °F). Under average conditions, the crop matures in 3–4 weeks, but it may take 6–7 weeks to mature in colder weather. Homegrown radish varieties are often significantly sharper in flavor. Radishes grow best in full sun in light, sandy loams with a soil pH of 6.5 to 7.0, but clayey-loam is ideal for late-season crops. Soils that bake dry and form a crust in dry weather are unsuitable and can prevent successful germination. Harvesting periods can be extended by making repeat plantings spaced a week or two apart. In warmer climates, radishes are normally planted in autumn. Seeding depth affects the resulting root size: 1 cm (1⁄2 in) deep is recommended for small radishes, and 4 cm (1+1⁄2 in) deep for large radishes. During the growing period, the crop needs to be thinned, weeds need to be controlled, and irrigation may sometimes be required. Radishes are a common garden crop in many parts of the world, and their fast harvest cycle makes them particularly well-suited for children's gardens. After harvesting, radishes can be stored without losing quality for two or three days at room temperature, and for about two months at 0 °C (32 °F) with a relative humidity of 90–95%. Radish seeds can be pressed to extract radish seed oil. Wild radish seeds contain up to 48% oil, which is not suitable for human consumption, but is a potential source of biofuel. Daikon radish grows well in cool climates; apart from industrial uses, it can be used as a cover crop to increase soil fertility, scavenge nutrients, suppress weeds, reduce soil compaction, and prevent winter soil erosion. A traditional Bavarian Oktoberfest dish called "Radi" is made of spiral-cut radish served with salt and occasionally chives, traditionally served with beer.
