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Seed Starting Calendar.
Seed Starting Calendar
Enter your last spring frost date. Get the schedule: when to start each crop indoors, when to direct-sow, when to transplant.
How to use this calendar
- Find your last frost date. NOAA, your county extension office, or weather.gov has this. It's the date after which spring frost is statistically unlikely (typically the 90% probability date).
- Start indoors = the date to sow seeds in containers under lights / in a windowsill. Most warm-season crops (tomato, pepper, eggplant) need 6-10 weeks indoors before transplant.
- Transplant out = the date to move seedlings outside. Some crops (broccoli, cabbage) tolerate cool soil and go out before last frost; warm-season crops wait until after.
- Direct sow = sow seeds straight into the garden. Beans, corn, root vegetables, and lettuce all work this way.
- Hardening off always comes between indoor start and transplant — typically a 7-day gradual exposure to outdoor conditions.
General timing rules
| Rule | Why |
|---|---|
| Cool-season crops: direct sow 2-4 weeks before last frost | Lettuce, peas, spinach, radishes germinate at 40-50°F soil; warm soil bolts them |
| Warm-season crops: transplant 1-2 weeks after last frost | Tomato, pepper, basil, beans need ≥55°F soil; frost kills them |
| Heat-loving crops: wait until soil is 70°F+ | Okra, melons, sweet potato, eggplant; 3+ weeks after last frost in cool regions |
| Brassicas: start indoors early, transplant before last frost | Cabbage, broccoli, cauliflower tolerate light frost; bolt in heat |
| Root crops: always direct sow | Carrots, beets, radishes don't transplant well — taproot damage causes forking |
| Fall succession: count back from first frost | For fall harvest of cool-season crops, sow ~10-14 weeks before first fall frost |
Soil temperature is the better signal
The calendar gives you statistical timing, but actual soil temperature is what matters for germination. A cheap soil thermometer at 4-inch depth tells you what your seeds will experience:
| Soil temperature | What can germinate |
|---|---|
| 40-45°F | Lettuce, spinach, radish, pea |
| 50-55°F | Beet, carrot, brassicas, parsnip, swiss chard |
| 60-65°F | Bean, corn, cucumber, squash |
| 70°F+ | Tomato, pepper, eggplant (best when transplanted, not direct-sown) |
| 75-80°F | Okra, melon, sweet potato |
Free under CC BY 4.0. Cite as "OAT Seed Starting Calendar (openagriculturetechnology.com)". Timing reference data from USDA extension publications and standard garden references.