I only use the freshest seeds possible. I have had bad or no experience with older seeds (like with Crocus). If I don't get the seeds until November or later, I use additional light to have a 12-hour day. Lots of light seems to be good. Substrate: lime or acidic, depending on the species. P. vernalis, for example, = silicate, P. vulgaris = lime. The seeds are only lightly covered with grit. If the tails move when moistened for the first time, the seeds are good. If not, I have had almost no germination so far. Germination should take place within 2-4 weeks. I then leave the light on over the winter until it is a 12-hour day outside again. That's what I do anyway. Others certainly have different experiences and there is always room for improvement :-)