Free interactive tool
Seed Starting Calculator
Count backward from your frost date — sowing dates are subtraction, not folklore.
Count backward from the frost date
Slide the last-frost week and the days to maturity; the timeline shows when to sow and when to expect harvest.
Planting dates are subtraction, not folklore: harvest week minus growing time equals sowing week, with frost as the boundary.
- Give a 90-day crop a late frost date. When must it be sown?
- Shorten to 45 days and see how much later you can safely start.
Planting dates are arithmetic: harvest week minus growing time equals sowing week, with frost as the hard boundary. Slide your last-frost date and the crop's days-to-maturity to see both ends of the season.
Use it per crop — a 45-day radish forgives late starts that a 90-day tomato will not.
When should I sow after the last frost?
A week after the average date is a common safety margin for tender crops.
What does days-to-maturity actually count?
From transplant (for started crops) or sowing (direct-sown) to first harvest, under decent conditions.