Greenhouse night temps

I have another greenhouse question for you people........what is the minimum night temperature I should shoot for? I was thinking 50 degrees for mature tropical plants. Ferns, brugs, hibiscus, etc. At this point I have no plans to start seeds and such, I will just be doing the plant wintertime boarding. Anyone with ideas?? Thanks. Oh, by the way, the GH is coming along very well. The insulation on the north wall and roof will be applied next week, as will the polycarbonate paneling on the south wall and roof. Here is a photo of the south roof, waiting for the paneling and rafters. The ventilation fans are installed, as are the motorized shutters.

Looking good Anna. I'm sure someone will be along to answer your question...I live in an area that doesn't get real cold in the winter.

Anna,

I think it will depend on the R-value of the polycarb and heat loss through the polycarb. The manufacturer should be able to provide you with that information.

Secondly, is the polycarb a double with an air space in between? If so that will give you a higher R-value. At 50 degrees in zone 6 I lost all of my brugmansia plants this past winter and it was a mild one for us. Your zone is even colder than mine so I think I might shoot for 65 degrees for winter temps.

I have my thermostat set on 45*, it got down to 42* a few times. I only lost a few orchids that were against the plastic and the temps got into the teens for a couple of nights. I use heat mats to start the seeds, these are set @72* and after the cold snap I put my orchids on these. Each mat is 2'X25'and costa about $25 per month in electricity to run. I heat the greenhouse with gas. My brugs bloomed all winter, in fact, nothing went completely dormant. I'm in zone 7a. You can use a min-max thermometer to keep a check on the temps in the green house.
BTW, my covering last year was single layer 6mil plastic, UV treated for greenhouse use. This year we are using two layers with a blower fan to keep them inflated. This should give me more insulation on the sides and keep the orchids from freezing in case we have another weird cold spell.

Cala,

Here it gets as low as -10 C and sometimes lower with the wind chill factor. You have the advantage of a dual heat system with heat coming up from the propagation heat mats and the gas. Plus your temps never really hit freezing very often so that's another factor. What does the thermometer read in the greenhouse with the dual heat? I'm guessing it would average out to be about 60-65 degrees. I wonder what Anna's temps are where she is in zone 4b. I image its pretty cold there especially at night.

Does your gas run on a separate line or does it come off your house? What do you average a month for gas payments. Gas for heating almost double here last year. Gasoline prices for cars are through the roof!! I'm considering a woodstove for the daytime and propane heater for evenings and night.

The min it got was 42*, that was registered on the thermometer hanging in the middle of the greenhouse, 5 feet off the floor. It would usually be 45* except on the coldest nights. My thermostat is hanging in the middle of the greenhouse too. The nights it was in the teens, the brug leaves touching the sides froze.
We used forced air furnace, all the gas for the greenhouses and garden center is on one meter. Our bill in the winter for the greenhouses can run $600 per month. Gas here was high last winter too, for both cars and heat.

Cala,
Okay, I see your night temps are still above freezing for the most part. Most nights last year here from Jan-April were around zero degrees and lower (conversion to F.) How many square feet do you figure the greenhouse and garden centre are? Are you able to compensate income for the garden center by staying open in the winter? Do your use that time to wholesale to other places? How many months do you actually remain open? I know that's a lot of questions.

The new greenhouse in the back garden will eventually be 3 stories. This year only the first level is going up. When my settlement for my law suit comes in I hope to put in a foundation with a basement where I can do all the propagating and growing. The main level I can then use for garden ornaments, seasonal displays and sales with the second storey for plant selections.

I don't have many years left before I hit retirement which is 65 here in Canada. I need to be able to contribute money into Canada Pension Plan in the meantime.

That's INSIDE the greenhouse temps, the outside temps got down in the 20's and 30's all the time, into the teens for a week.

Most growers reccommend no less than 55F at night for Hibiscus etc. some kinds will atke less..but is risky..

Eclipse, glad you mentioned that, they will have to go into the fern house!! I kept one large pink hibiscus in there last year, it did okay, lost it's leaves but put back out great in the spring. Should I bump the temps up to 55* this winter? Would it make my pods ripen faster? They took forever last winter.

Kyle, That's good to know. Cala, okay now I understand. duh sometimes I'm slow especially when I've had my grand daughter for a sleepover.

We have cold temps here in the winter. I tried keeping the growth of the Brugs slowed down by keeping it cooler in the GH.The temp in the GH usually ran 60-65 in the daytime and 50-55 at night.There were a few extremely cold nights that it got down to 46-48 inside the GH.I have 6 mil greenhouse plastic and a gas heater in the GH.When it went below 0 some of the leaves that touched the plastic were frost bit but I didn't have any other problems keeping it cooler in the GH at night.

sure didn't slow them down snow!!!

Brug pods ripen at their own rate...obstinate little buggers they are.. pods set in the spring ripen by fall pods set in the fall ripen near spring.

Boy, I am so jealous of your greenhouses! My property is so steep that there is no place to put one. But I have an alternative. I run the archives for my county in a large mansion. There is a big landing on the stairs with lots of wide window-shelving, meant for plants . I can put a few there and it's heated. It's pretty dry though and I have to water and mist when I'm there on Tuesdays and Fridays. The seniors still meet downstairs at their mealsite, which I used to manage until I fell and injured my back. After a year of worsening arthritis, I had to quit. They love the plants, though.

LOL tiG, no it didn't slow them down. Not one bit. I'll have to try something different this year.

Snowhermit,

You are in the same zone as Anna-zone 4. I think it would be best to Anna to set her temps like your or perhaps just a little higher.

Woodspirit,
I came across a website for a greenhouse on a sloped property. All you need to do is install a foundation retaining wall on the lower slope or install on posts to compensate. You can make the floor level by putting in a wood floor with waferboard. Mine has a gentle slope that drops about 16" over a run of 22 feet so I'm installing a waferboard floor. Mine will be on posts and the slope will still be able to drain properly.

joydie, It would depend on what Anna has growing in her GH. This worked fine for the Brugs but when I started seeds the year before I had it set to 70-75 degrees.Some plants need warmer temeratures.

Snowhermit,
She only wants to overwinter plants and has no plans of seed starting according to her original post.