How to Grow German Giant Radish
Raphanus sativus 'German Giant'
German Giant Radish is a popular heirloom root vegetable known for its rapid growth and large, crisp yield. Gardeners prize this cool-season crop for its ability to thrive in cooler weather while delivering a sweet crunch that makes it ideal for salads or roasting.
📷 Wikimedia CommonsStarting German Giant Radish: indoors or direct sow?
🌾 Sow directly in the garden — German Giant Radish is not usually started indoors.
Direct sow seeds outdoors two to six weeks before the last frost date; transplanting seedlings is generally unnecessary and may damage the sensitive taproot.
Soil, care & harvest
Prepare loose, fertile soil with a pH between 6.0 and 7.0 to encourage strong root development. Sow seeds directly outdoors two to six weeks before the last spring frost date, as this plant tolerates light frosts well. Plant them about one inch deep in rows spaced four to six inches apart. Germination typically occurs within four to seven days under cool conditions.
Space seedlings four to six inches apart to allow roots room to expand without crowding. Keep the soil consistently moist, aiming for about one inch of water per week, as dry spells can cause splitting. Apply a light mulch to retain moisture and suppress weeds, but avoid piling it against the developing roots.
Watch for flea beetles, cabbage root maggots, and aphids; encourage beneficial insects or use row covers early in the season to prevent damage. Clubroot and black rot can be minimized by practicing crop rotation and ensuring good drainage. Harvest the large roots forty-five to sixty days after sowing when they reach their prime size.
When to Plant German Giant Radish
Planting windows vary by USDA hardiness zone. Look up yours by ZIP code.
| Zone | Start Indoors | Direct Sow | Harvest |
|---|---|---|---|
| Zone 1 | — | June – July | July – September |
| Zone 2 | — | May – July | July – September |
| Zone 3 | — | May – June | June – October |
| Zone 4 | — | April – June | June – October |
| Zone 5 | — | April – May | June – November |
| Zone 6 | — | April – May | May – November |
| Zone 7 | — | March – May | May – November |
| Zone 8 | — | March – April | April – December |
| Zone 9 | — | February – March | March – December |
| Zone 10 | — | January – March | March – December |
| Zone 11 | — | January – February | February – December |
| Zone 12 | — | January – February | February – December |
| Zone 13 | — | January – February | February – December |
Companion Plants for German Giant Radish
✓ Good companions
Radishes mature quickly and loosen soil for slower-growing carrots
Repels root maggots and other soil pests that damage radish roots
Radishes deter cucumber beetles and striped cucumber beetle
Shallow roots don't compete with radish taproot, radish breaks up soil for lettuce
Deter nematodes and other soil-dwelling pests harmful to root vegetables
Trap crop for flea beetles and aphids that commonly attack radishes
Fix nitrogen in soil and have different root zones, reducing competition
Compatible growing requirements and harvest times, efficient space usage
✗ Keep away from
Same family plants compete for nutrients and attract similar pests like flea beetles
Can inhibit growth of radishes and other root vegetables through allelopathic compounds
Both are root vegetables competing for same soil space and nutrients
Nutrition Facts
Per 100g serving (USDA FoodData Central)
