USDA Zone 1 planting calendar
When to plant radishes in USDA zone 1
Sowing, transplant, and harvest dates calibrated to zone 1's 60-day season (Interior Alaska (Fairbanks region)).
Key dates for radishes in zone 1
| Stage | When | Anchor |
|---|---|---|
| Direct sow outdoors | late May (May 25) | 21 days before last frost (mid-June) |
| First harvest (estimate) | late June (June 22) | ~28 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 1
Zone 1 has average annual minimum temperatures of -60 to -50°F and a 60-day frost-free window from mid-June to mid-August. Radishes 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 1.
Radishes are the fastest root crop — spring types mature in 22-30 days from direct sowing, making them ideal row-markers alongside slower crops. Sow 2-4 weeks before the last spring frost as soon as soil can be worked; they bolt and become pithy and peppery hot if left too long in warming soil. Succession-sow every 7-10 days for a continuous harvest; daikon and winter types sown in late summer take 50-70 days and tolerate heavier frost.
Quick-grow guide
- Sun: Full sun — 6+ hours direct.
- Soil temperature for germination: 7-29 °C (45-85 °F).
- Spacing: 2-3 inches (5-8 cm) between plants.
- Days to harvest from direct sow: ~28 days.
- Plant in cool weather and provide afternoon shade once temperatures climb above 24 °C.
Common mistakes — zone 1 × radishes
- Planting before last frost: zone 1's last frost averages mid-June, and even a light frost will kill radishes seedlings overnight.
- Skipping hardening off: even healthy indoor transplants need 7-10 days of progressive outdoor exposure before going in the ground.
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 radishes — full guide
- USDA Zone 1 — frost dates and what else to plant
- All 13 USDA hardiness zones