Seed Stratification Planner
Count backwards from a sowing date through your seed's ordered treatment stages. Build warm, cold or other treatment reminders using supplied durations.
Starts with an editable example. Replace the dates and rules with your own.
Your calculation
Ready when you are
Choose your dates.
Select your counting rules and calculate.
Calculation details
| Step | Value |
|---|
How to use this calculator
Enter the sowing date and treatment stages in the required order. Each stage uses the full calendar-day duration you provide.
The final treatment ends the date before sowing. Earlier stages run consecutively with no unentered gaps. Labels and durations come from your seed instructions.
A worked example
Fourteen warm-stage days followed by thirty cold-stage days before April 15, 2027 sowing require a March 2 start.
Does the calculator prescribe cold treatment?
No. Species and seed lots differ. Obtain treatment instructions separately, then use the planner to arrange those stages.
Which calendar and years are supported?
Use Gregorian dates from 1900 through 2100, with results in that range. Daily plans allow up to 366 dates; dark-sky searches allow 31 nights. Durations, capacities and policy rules are supplied by you. Astronomy uses the bundled Astronomy Engine, sea-level geometry and browser time-zone rules. Timed exports use UTC instants; date-only events do not assign a clock time. Copy, CSV and print include calculation assumptions. Nothing is booked or scheduled outside this page.
What happens to my dates?
Calculations run on your device. Saving a calculation is optional and keeps it in this browser. A setup link contains the dates and settings you entered; anyone with the link can read them. Use one tab per saved calculator. Clear saved data from Privacy & settings.