① For a spring planting, sow seeds 4–6 weeks before the average date of last frost. It’s best to plant radish seeds directly in the garden so as not to disturb their roots.
② Directly sow seeds outdoors ½ to 1 inch (1-2 cm) deep and 1 inch (2.5 cm) apart in rows 12 inches (30 cm) apart.
③ Plant another round of seeds every 10 days or so—while weather is still cool—for a continuous harvest of radishes in the late spring and early summer.
④ You can plant radishes later than any other root crop in late summer or early fall and still get a harvest. Sow seeds 4–6 weeks before the first fall frost.