Mine do great at 55 or 60 at night & up to 80 in the daytime.This is in a greehouse. Lots of air circulation.It is hardest to keep it cool on bright sunny days.
rose

the hotter it is.. the faster they grow.. and can become leggy ...

your biggest problem.. is timing this out.. to when you can take them outdoors..

forcing them fast and big.. you may end up with really ugly plants.. and have to keep them in the house for 2 extra weeks.. while the outdoor temps come up to speed ...

err towards cool and slow ... which is root growing temps..

and if you fert.. get a formula toward root growth.. and low toward flower.. again.. dont zoom them the wrong way ...

you didnt realize this is all much more complicated than introducing seed to media.. and adding water .. did you ???? .. lol .. reminds me of my first attempts ... lol

have you figured out the best time to pot them all up from the seed flat.. and how you will maintain 200 odd pots???? .. you cant leave them all in the flat.. or you will have a nightmare trying to separate roots ... send me an email if you want a pic of how i used to do it.. i will be gone for a few days.. and dont want to forget.. IF you are interested ... no time now...

ken

Thanks folks! Although I've been starting both vegetable & flower seeds for several years, this is my first attempt with pets.... And yes, Ken, it (ie,growing from seed) sure is more involved than one might originally perceive!