This is the first winter for my greenhouse, but I would bet the farm that it's going to be below freezing pretty much every night, but warm up during the day. It's this temp swing I'm worried about. Last year I built a box that hung on the side of the house in front of the kitchen window. The box had a glass top and no back. This is the one I was thinking of using. I wintered my more gentle trees in it and left the slider window in the kitchen open about 2 inches to get some heat from the house. My wife, was not impressed. In the past, I have left my trees outside in a box I built out of styrofoam without a lid. I then filled it with leaves in a wind sheltered area. It worked fairly well for most of the trees, but I did loose a few. STA4...are the heating cables you used designed to go under soil or would the type you put on the roof to melt snow work? I would assume the ones for the roof would not have a thermostat. Thanks for the input. Jim

I am using the water bottle system...I have several bottles that I filled wth salt water NaCl...I probally have about 30 bottles total and 3 wiith NaCl...I am growing orange, lemon trees...they are small and fragile...they are showing good growth...and all leaves are very healthy....it has been below 40 at night in the GH...so tropicals can survive below 50...and do good...I have a smalll fig tree...bought it late and didnt want to put it in the grown at that early stage due to winter damage...I have 7 figs on it and it is developing new leaves like crazy.. I have 6 tomatoe plants which I am have started to produce tomatoes...not many but even during the summer fiirst production is always slow....I have a peppercinno plant in therer which has also started to flower....along with 2 hybiscus the troppical kind which hasnt shown any cold stress...Keep in mind I have no heat and the outside temps has been in the 20's at times and GH temp has been below 30...none of the water bottles has froze..whiich I was surprised...I do get ice on the inner walls...but it hasnt bothered the plants...as long as they dont touch the wall....from what I can tell the soil hasnt froze either....and some contaniers arent really that big...I have some 2 inch container...I do not completely understand this...but it is cool..I have come to the conclusion that there seems to be no need for heat in a small GH..as long as it is fillled with plants...soil bags....anything that will hold heat....ohh yeah the salt water contaiiners stay warmer longer...I need to get a thermometer probe to do further research on this issue...but it is very cool...I think atleast.. Steve

Hi All, Thanks for your response. Cactusfreak - where did you purchase your pool cover? I have been planning on getting one of those eventually. When I bought the greenhouse I thought it was much more insulated and a lot of people (including the distributor), told me it would be more than warm enough with two oil radiators. It sounded like I would need more heat than that, but I thought it would work out. I think what I will do for this winter is insulate the greenhouse like crazy, get a good heating system and hope for the best. I'll have to look up Pittsburgh's weather records as well for the winter. If it doesn't work I'll just use it as a cold frame. I will be growing a bunch of orchids in the greenhouse and a handful of 'annuals' including Fushia, hibiscus, mandavilla and more. Some of the orchids are probably the most sensitive to the cold.

I believe the claim of 95% UV reduction. That's necessary to protect the covering itself. The coverings lacking a UV blocker are destroyed in short order. The only disadvantage I've heard about is bumblebees may not do as well under some coverings due to light exclusion that they need to navigate. I don't think lack of UV will affect plants. But greenhouse plants still might need some hardening off when going outside. No direct IR simply means as you suggest that it has been diffused. This might reduce heat stress on some plants but I've not seen much damage under clear polycarbonate with 90% transmission. Max heat gain by day will likely translate to max heat loss at night. In my climate two layers inflated of woven poly reduces both heat gain by day and heat loss at night. A plus here but we have lots of sunny warm days all winter..