Sowing Date
Plan a sowing and harvest day from days to maturity.
About Sowing Date
Seedlings started indoors are moved out around the frost date, so the sowing day backs up from frost by the start lead time. Back-counting from frost and maturity keeps transplants ready on time, which is the difference between a full and a wasted season.
Formula
Sowing Date
Sow day = last frost - sow-before; harvest = sow day + days to maturity
- sow-before
- Lead time seeds need to start indoors before frost
Worked example
With the default values below, Sowing Date returns Start Seed Day (of year) of 70. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Last frost day of yearaccepts 1–365
- 120
- Days to maturityminimum 0
- 70
- Sow days before frostminimum 0
- 50
Results
- Start Seed Day (of year)
- 70
- Harvest Day (of year)
- 140
Step by step
- 1Values used
- 2Sowing Date
- 3Start Seed Day (of year)= 70
- 4Harvest Day (of year)= 140
Assumptions and limits
- The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to whole numbers, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is Sowing Date calculated?
Sow day = last frost - sow-before; harvest = sow day + days to maturity Seedlings started indoors are moved out around the frost date, so the sowing day backs up from frost by the start lead time.
Why does Sowing Date matter?
Back-counting from frost and maturity keeps transplants ready on time, which is the difference between a full and a wasted season.
What values do I need to enter?
This calculator takes 3 inputs: Last frost day of year, Days to maturity, Sow days before frost. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.