Red Onion — Growing reference
| Scientific name | Allium cepa |
|---|---|
| Seed germination (days) | 10–14 |
| Soil temperature for germination (°C) | 15.6–23.9 |
| First harvest or flowering (days) | 100–120 |
| Measured from | Transplant |
| Plant spacing (cm) | 10.2–15.2 |
| Mature height (cm) | 45.7–61 |
| Mature spread (cm) | 10.2–15.2 |
| USDA hardiness zones | 2–11 |
| Light | Full sun |
| Water | Moderate |
| Sowing method | indoor-start |
Growing directions
Grow identically to yellow onions, starting seeds indoors 10–12 weeks before transplanting or planting sets as early as soil can be worked in spring in well-drained, fertile soil in full sun; red onions get their distinctive color from anthocyanin pigments concentrated in the outer layers and are the premier choice for fresh use in salads, salsas, pickles, and raw preparations where their mild, slightly sweet flavor and dramatic purple-red color provide visual impact alongside their culinary role. The color fades when cooked, making them less suitable for long-cooked dishes than yellow onions. Popular varieties include 'Red Burgundy' (short-day, for zone 7–10), 'Red Wethersfield' (long-day, for zone 3–6), and 'Redwing' (intermediate-day). Quick-pickled red onion in lime juice or vinegar is one of the most versatile condiments in modern cooking.
Source and local conditions
Typical planning ranges from OpenPlantDB (CC0). Cultivar, climate, season and growing method can change these values. Confirm the seed label and local guidance before planting.
Source & verification
OpenPlantDB · CC0