I sowed three different varieties of marigolds on 27/March and I am getting awful germination rates: 0% to 20%. This is much worse than any of the other seeds that I've sown around the same time - even so-called tricky to germinate kinds.

Does anyone have any tips? Do they need to be sown head-down? Surface sown? Tails removed? Something else?

Mine were sown into Pro-Mix potting & seeding mix, either scattered on the surface or lightly covered. No bottom heat was applied, but the room is fairly warm (15-20 degrees C or 60-70 Fahrenheit).

Thanks!