Radishes prefer the cool temperatures and short days of spring and late summer. Long-rooted types can tolerate heat and long days better. Plant in cool to warm soil (50-80F), 1/2 inch deep in rows 8-12 inches apart. Thin to 2 inches once germinated. Radishes are best grown quickly with plenty of water, and harvested promptly when ready as they do not 'keep' well in soil. Fertile soil, cool temperatures, and consistent moisture will yield the best crops. Plant in succession for an extended harvest.