I used to get so frustrated with my Nigella seed when it was germination test time.
We would test 100 seeds but barely any of them would sprout. But I knew that if I were to sow these seeds in the field, they would all germinate.
One year we tested Nigella germination at 15C instead of in our warm germination chamber and those seeds sprouted so quickly.
Now we pay a lot more attention to what temperature we run germination tests.
There are 3 main temperature groups.
30C Daytime and 20C Nighttime
We test these seeds in a fridge that isn’t running. We’ve added an incandescent light bulb into the bottom of the fridge to act like a little sun.
Day Phase: The light bulb is on a timer so it only turns on for 8 hours. It is also on a thermostat, so that the light bulb turns off when the fridge temperature goes over 30C.
NIght Phase: We let the fridge cool naturally until it goes down to 20C (close to ambient temperature).
Crops in this temperature range include: Amaranth, beans, brassicas, beets, chard, basil, oregano, thyme, zinnia, sunflowers, okra, tomatoes, peppers, eggplants, squash, cucumbers, melons, carrots, parsley

20C all the time
We leave these germ tests out at room temperature.
Crops in this temperature range include: Onions, leeks, peas, lettuce, celery
15C all the time
We’ll put these in a vegetable or seed cold room that is set at 15C.
Crops in this temperature range include: Orach, spinach, nigella, poppies, mâche
Many seeds will still germinate if they are in the wrong temperature range.
But they will take much longer to do so. If you want quick germination, get those seeds at the right temperature!!!