Work out seed starting date instantly with clear inputs, formula shown and shareable results.
The sowing date counts back from the last frost date by the recommended indoor growing weeks, and hardening off starts a set number of days before planting out. Sowing too early produces leggy seedlings that cannot be planted out, which is why counting back from the frost date beats sowing on a fixed calendar day.
Sowing date
sow date = last frost date - weeks indoors x 7 days
sow date = last frost date - weeks indoors x 7 days. The sowing date counts back from the last frost date by the recommended indoor growing weeks, and hardening off starts a set number of days before planting out.
Sowing too early produces leggy seedlings that cannot be planted out, which is why counting back from the frost date beats sowing on a fixed calendar day.
Enter expected last frost date, weeks to start indoors before that date, days to harden off before planting out. The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.