Awww, that's nothin'! It can get over 100 here for days in a row, with a "break in the heat" being a dip down to 95 or so. This goes on for 3-4 months, with a long stretch of high 80's / mid 90's book-ending on both sides of the really hot part of summer. I wouldn't worry about those fluctuations from night to day, or day to day, that's natural. All of my plants are fine with it, except Fuchsia, but I don't think you have one of those anyway. Everything else grows like crazy in the summer. Nothing gets much sun from about noon-1:30, except Sans. Everything is placed to get either morning sun before that, or afternoon sun (a lot hotter, especially for roots in a dark pot.) When in doubt, go with morning if you have the option there. Back it up a bit if you see some sunburn. My plants have been outside since mid-March. Once they go out, they don't come back in except in the case of frost which, if I've decided correctly on which day to do this, won't be until winter. The weaker the sun rays are when they get out there, the easier it is for them to adjust to much more sun, gradually as its' angle changes. I know that's way too early there, but just wanted you to have the info for reference, confidence. And I know you're the type to take them in & out, very useful in Z4. Look how lucky we are, supposed to be cooler all week until the weekend! We've almost hit 100 here a couple times already. If you click the blue "monthly" at the left, check out the end of last month.

70-75 is a good germination temp for most things but it needs to be consistent until they sprout. They may still sprout eventually but it will take much longer and you risk the seeds rotting without that consistent soil temperature. All you can do is give it a try. ;) Dave

Where are you measuring the temperature? Amoungst the plants or at the top of the roof?

Three things that I note in professional/commercial greenhouses that I see lacking in most 'home' greenhouses (including mine) - 1. circulation (i.e. fans) 2. vents that are thermostat controlled 3. drip irrigation on timers. I'd look into the vent issue and see what the manufacturers set up their vents/thermostats at to get a flavor how much heat is too much heat. I just burned out a bunch seedlings in my greenhouse, as I had NO idea how hot it would actually get in there. My answer - really darn hot! Seems to me that tropical clumpers, on the whole, would love the warmth on the roots as well as the humidity, of a greenhouse. But care should be taken not to flood and drown the roots.