The Radish (Raphanus sativus) is an edible root of the Brassicaceae family. There are numerous varieties of radishes – varying in size, color, and in days to reach maturity in the garden. Radishes grow best in full sun in sandy, loose soil with a pH 6.5 to 7.0. The depth at which seeds are planted affects the size of the root – from ½ inch deep recommended for small radishes to 1½ inches deep for large radishes. They are in season from April to June and again in the fall in most parts of North America.
Radishes serve excellently as Companion Plants for many other vegetables because of their ability as a “trap crop” against pests like flea beetles. These pests will attack the radish leaves, but the root remains healthy and can be harvested later.
In general, there are two types of radishes – Spring Radishes; and, Winter Radishes:
1. Spring Radishes germinate quickly – most of them in just 3 to 7 days – and they typically reach maturity in 3 to 4 weeks. Their fast growth cycle makes radishes a favorite choice for childrens’ gardens, too. Harvesting radishes can be extended by planting them every two weeks from early spring until a few weeks before the first frost EXCEPT during the summer periods of hot weather. In southern warm-weather climates, they are mostly planted in the fall and early spring. Besides the large selection of Spring varieties, there are a limited number of Summer Radish varieties – for example, French Breakfast and Icicle – that can better tolerate warmer temperatures.
2. Winter radishes are sown in midsummer to late summer, much as fall turnips, and they are slower to develop than spring radishes. Winter radishes grow considerably larger, remain crisp longer, are usually more pungent, and they hold in the ground and store longer than spring varieties. A widely popular type of winter radish is Daikon, which refers to a broad selection of winter radish varieties from Asia. Daikon radishes are sometimes called the Japanese radish, Chinese radish, or Oriental radish, and they usually have elongated white roots.
Spring and Winter radishes are both rich in ascorbic acid, folic acid, and potassium. They are a good source of vitamin B6, riboflavin, magnesium, copper, and calcium. Radishes are typically eaten raw; however, they can be steamed to soften the flesh. In fact, the entire plant is edible since the leafy tops can be served as a leaf vegetable. Radishes are also grown for use as sprouts.