USDA Zone 11 planting calendar
When to plant onions in USDA zone 11
Sowing, transplant, and harvest dates calibrated to zone 11's 365-day season (Florida Keys, Hawaii (most), Puerto Rico, southern California (coastal)).
Key dates for onions in zone 11
| Stage | When | Anchor |
|---|---|---|
| Direct sow outdoors | October — February (the cool dry season is your spring) | No frost — plant in the cool months |
| First harvest (estimate) | ~110 days after sowing | ~110 days from sow |
Dates are zone-wide averages. Local microclimates (south-facing slopes, urban heat, lakeside warmth, elevation) can shift the planting window by 1-2 weeks within the same zone.
Why this timing works for zone 11
Zone 11 has average annual minimum temperatures of 40 to 50°F and a 365-day frost-free window from no frost to no frost. Onions are hardy enough to handle light frost — and in fact prefer cool weather. They bolt or turn bitter once daytime temperatures consistently climb above 24 °C, which is why earlier is better in zone 11.
Onions are day-length sensitive: long-day varieties (zones 1–6) begin bulbing when days exceed 14 hours, short-day types (zones 7–10) bulb at 10–12 hours, and intermediate-day varieties span zones 5–6. Start seeds indoors 10–12 weeks before the last spring frost and transplant out 4–6 weeks before it — young onion seedlings tolerate frost down to about -6 °C once hardened off. In zones 8–10 a second planting from sets in autumn is common, overwintering for an early-summer harvest.
Quick-grow guide
- Sun: Full sun — 6+ hours direct.
- Soil temperature for germination: 10-35 °C (50-95 °F).
- Spacing: 4-6 inches (10-15 cm) between plants.
- Days to harvest from direct sow: ~110 days.
- Plant in cool weather and provide afternoon shade once temperatures climb above 24 °C.
Common mistakes — zone 11 × onions
- Spring planting: zone 11 springs are too short — sow onions in autumn for a winter and early-spring harvest instead.
- Waiting for "warm" soil — these crops germinate at 7-10 °C and bolt the moment summer heat sets in.
Source and methodology
Frost-date averages from NOAA Climate Data Online within each USDA hardiness zone. Hardiness zone boundaries from the USDA Plant Hardiness Zone Map (2023). Crop timing offsets calibrated against US Cooperative Extension Service publications (UNL, UMN, NC State, Texas A&M, UF/IFAS) and cross-checked against the RHS sowing calendar for en-GB readers. Curated by the Growli editorial team.
Keep going
- How to grow onions — full guide
- USDA Zone 11 — frost dates and what else to plant
- All 13 USDA hardiness zones