Growing radish crops is considered one of the easiest vegetables to cultivate, and they can be grown successfully either outdoors or in containers. A general recommendation is that radishes like cool temperatures between 50° to 70° Fahrenheit (10° to 21° Celsius), so they are best started in the spring or fall instead of in the heat of summer. The various approaches to growing radish seed offer a quick learning process, however, as the plant matures in about a month's time, so it is a good plant for children to learn how to grow before trying to cultivate more difficult vegetables. The main requirement when planting radishes is that the soil in which they are kept be moist, since they are a root crop that directly depends on the water supply in the soil to increase in size.
Though radishes can come in different strains and colors, from red to pink and white, they all have similar growing conditions. Since a growing radish will mature in a month or less, subsequent crops of them can be planted at certain time intervals, so harvesting radishes can continue throughout the year. If they are being planted in the spring, they should be started about two weeks before the last significant frost and then new plantings done every ten days, as they will mature a bit faster in the spring than in the fall due to more direct sunlight at the start of the year. When growing radish crops in the fall, they should be planted every two weeks, starting at a point about two months before the first strong fall frost hits the area.
The ground in which radishes are planted should have good drainage and steady rainfall or be watered regularly. This might involve introducing compost or sand into the ground if it has a high clay content. Once the seeds are planted, if the soil is warm and moist, they should germinate and sprout through the surface in half a week to a week's time. Seed should be planted to a depth of 0.5 inch (1.3 centimeters) and spaced about 1 inch (2.5 centimeters) apart, as the plants themselves don't get too large above ground. As the growing radish crop matures, some can be picked as small samples for salads with other remaining as plants allowed to spread out and grow larger.
There are several issues that can arise when cultivating the radish. The few insect pests that prey on a growing radish can be defeated by placing a breathable cover over the surface of the plants as they grow, and this will help keep them moist as well. Another problem that may arise, though it is uncommon, is that, if the temperature is too cold, a growing radish may flower early instead of producing sizable roots. If they are over-watered or receive excessive amounts of rainfall, radish roots can also crack, but this does not harm them as a food source in any way.
Radish seed can be saved for up to five years if the plants are allowed to flower and the seed pods to turn brown and dry out. Once radishes are picked, their flavor can also be enhanced by soaking them in ice water for a few hours before eating them. As a container crop or for a child's first garden experience, a growing radish needs the same conditions as an outdoor variety. The main thing to watch for is the temperature, as a continuous exposure to temperatures of 75° Fahrenheit (24° Celsius) or higher causes radishes to flower and quickly go to seed before they are mature just like excessively cold temperatures will.