Start radish prep as early as your soil can be worked, as much as a month before the last expected freeze.Like all root vegetables, radishes prefer loose, well-drained soil. Drag your trowel lightly to create a 1⁄2-inch-deep line for planting. Sow seeds about an inch apart, and then smooth the soil over the seeds. Allow 6 inches between rows. Water well and wait, but not for long. Seedlings will emerge in a few days. A helpful tip: Label your radish rows with the date you planted them to help you know when they’re ready to harvest.