For urban gardeners eager to grow their own crisp radishes, one of the most common questions is about container depth. The good news is that radishes are perfectly suited for shallow planters. Generally, a planter box with a depth of 6 to 8 inches (15 to 20 cm) is perfectly adequate for most small round radish varieties. For longer varieties like French breakfast or daikon radishes, aim for a depth of 10 to 12 inches (25 to 30 cm).
This shallow requirement is because radishes are a fast-growing, small-rooted vegetable. The primary focus should be on providing loose, well-draining soil to prevent the roots from becoming stunted or misshapen. Ensure your planter has sufficient drainage holes to avoid waterlogging, which can cause rot.
Beyond depth, spacing is crucial. Sow seeds about 1 inch apart and thin seedlings to 2-3 inches apart to give each radish enough room to bulb properly. With the right depth, good soil, and full sun, you can harvest a vibrant crop of radishes from your balcony or patio in just 3 to 5 weeks.