- 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. Directly sow seeds outdoors ½ to 1 inch (2 cm) deep and 1 inch (2.5 cm) apart in rows 12 inches (30 cm) apart.
- 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.
- Plan on a fall planting. 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.
- Thin radishes to about 2 inches (5 cm) apart when the plants are a week old. Crowded plants do not grow well.
- Consistent, even moisture is key. Keep soil evenly moist but not waterlogged. A drip irrigation system is a great way to achieve this.
- For most varieties, harvest when roots are approximately 1 inch in diameter at the soil surface. Pull one out and test it before harvesting the rest!