Dear David, There are some seeds that require a change in temperature to germinate (a difference between day and night temperatures) and some need cold. Many South African bulb species from the winter rainfall area for instance (not Amaryllids) often need the former as that is what the weather is like during the time they normally germinate. Generally the advice is to start winter rainfall species in the fall and summer rainfall species in the spring and obviously the temperatures would be different for each to a degree. There are some seeds that need to be started right away. I start some things needing the daily fluctuation in temperature in my greenhouse as that makes it easier to provide warmer day temps. I don't heat my greenhouse so it is cool at night. The greenhouse also gives some protection from the excessive rain we get that some seedlings don't like. But other things I just start outside and then I don't have to worry about changing their environment later. On this list we have found that there is not just one way to grow from seed however. Some people float seeds, some use the paper towel method, some start in vermiculite in the fridge, etc. One of our first topic of the week discussions was on growing from seed. You'll find the link to some of those discussions here. http://pacificbulbsociety.org/pbswiki/index.php/… Hopefully you'll share which things you found did well with your system. Mary Sue > It's just a low-power plastic heating pad, which keeps the seeds warm.