Your real problem is that unless you are planning to insulate the living H out of it, you are looking to heat what is in essence, just a very large tent. There are any number of options and it can be done, but beyond the cost of the heater itself, you should also consider the cost of the fuel or electrical power to operate it. If you want to operate a heated GH in winter, even in Z-6; to maintain a steady 50 deg. interior temp. 24/7, you might want to reconsider either the size and/or type of GH you plan to erect, or expect to spend a whole bunch of money to run the heater.

Thanks gary. It's a tropical purple pygmy from Trickers. I decided to just lower it. The actual top of the container is now still just about 10" under the surface, so I think it will be okay. I had another small hardy lily that was probably still too close to the surface and had lots of floating leaves. I sank it yesterday and now the leaves are floating on the surface........which was really fast.........so I think they will all be okay. These are just 100 and 300 gallon stocktanks, so when they're even on the bottom, they are still relatively close to the surface.......as compared to a deeper pond. I've just been amazed in the past, with regular sized waterlilies in these ponds, how many more blossoms they had when they are on the bottoms and not just below the surface. Thanks again Gary.

Hey yellow thumb, where do you put your Michelia Alba in the winter? In a sunny room??? Do you have to watch for spider mites? I hear they love that plant. I will give you my address if you don't have it. How is the jade doing? So good to see you. You have to make the time. You are so missed here and have so much to offer along with your beautiful plants. As for your trees, if you don't mind them slowing down or loosing their rich green color, those temps will be fine as long as you know you watch your watering and I already know you use very ood mixes. In fact, it's much better than being in a dry heated house this early...Just make sure to acclimate them indoors if that is what you plan to do. Are you going to put them in a heated home in a sunny window, or a cool place? If a cool place you will not have to acclimate them...

I have never heard of humidity spots. Sun spots, mechanical damage, spots of unknown origin, yes. Humidity spots? Maybe due to damp conditions, where there is always water dripping down, causing a bit of fungus on the leaves? I have no clue. I don't greenhouse mine, but the humidity in my plant room (when they are inside) hovers between 50-75%. No water dripping, even when I mist. There is enough humidity for windows to condense a bit, but I don't know what humidity spots are.