Easy to grow from seed, radishes germinate quickly and are often ready for harvest in just a month. They're one of the first vegetable crops to harvest in late spring. Radishes are favorites for eating raw on relish trays and in salads. Oblong-shaped radishes are ideal for dipping. Cooler temperatures promote milder-flavored roots, so it's best to grow radishes as a spring or fall crop. Because they germinate so quickly, radish seed is often planted with carrot, beet and lettuce seed to mark rows. Tillage radishes, which are much larger than the globe-shaped red radishes, are used as cover crops. Like most other vegetables, radishes perform best in full sun and well-drained soil.