For some species (like lettuce, celery and pansy) germination at high temperatures (>25°C or 77°F) can induce thermo-dormancy.

Seeds with thermodormancy will not germinate when the temperature returns to near optimal temperatures.

Seed priming is an effective treatment to prevent thermo-dormancy.

Thermodormancy in pansy



10°C 75%
15°C 85%
20°C 90%
25°C 84%
30°C 56%
35°C 10%