Budget some cash for heating. Fuel is outrageous! Trying to keep the root zone above the "absloute zero" of 50 degrees is admirable. There are days in Jacksonville when it does not get out of the thirties!I let em' do the "cold storage thing" by cutting back on the water and letting them go into semi-dormancy.
I have allowed them to get a bit too cold (27 f), but all was well after adding two more 100 watt light bulbs. I know I'm losing some winter growth flushes by doing this, but the money I save in electricity I use to buy more citrus.
My enclosed (in winter) porch set up is only 5 x 8. The collection has grown and so have the trees, so it looks like I'm going to have to build a greenhouse of my own as well.
What is your choice of materials? I've acquired ninety sheets of 20 x 60 storm windows and some twenty foot aluminum sailboat boom extrusions for framing. I still think I'll do a "just above freezing" setup.

hairmetal4ever ..If you seach some of the most common posts youll find one by Tams, Millet offered some good information that you may find of interest..Dale

Better yet...close the house in the winter and move into the greenhouse :)

Hair, I have a 32 X 70 double poly greenhouse with air blown inbetween the two layers of polyethylene to keep the two layers of polyethylene covering separated approximately 2 inches apart. The air space between the two layers of poly is, of course, for additional insulation. I keep my greenhouse at 60 degrees night temperature throughout the entire winter. I have bananas, papays, 48 varieties of citrus trees, tomatoes, palms trees, pomegranates, figs, a guava collection, pineapples, orchids, and so on. The heat bill is what it is. All my benches are made up of black plastic south facing 55-gallon drums filled with water to absorb heat from the sun and painted white on the north side of the drum to reflect light around the greenhouse. The foundation all around the greenhouse was trenched four feet deep and filled with 2 inch styrofoam insulation to insulate the soil inside the greenhouse from the frozen soil outside. This makes the entire soil mass inside the greenhouse a heat sink. The greenhouse is aligned in a north south orentation, an orentation that gets the most light. The north wall is solid and insulated,(as north walls lose light and heat) and painted white to reflect the winter light coming from the south sun back onto the plants. The greenhouse is heated by two modine propane heaters. One heater set at 60F and a back up heater set at 50F just in case the first heater has a failure. In total the greenhouse has 650 gallons of internal water mass to absorb heat during the day. During the night the water, of course, cools down thus releasing heat into the greenhouse. I also have four roof box fans placed along the peak of the greenhouse, blowing all the heated air that rises to the top of the greenhouse back down to the floor. This also keeps the temperature difference between the inside top of the greenhouse and the cold outside air as close as possible, which greatly reduces the radiation of heat exchange going from the warm inside to the cold outside (as heat radiates from warm to cold). Fill free to e-mail me if you have any questions when you start you greenhouse.- Millet

Millet what kind of usage do you have with propane? what size tanks are you using? Do you have yet an estimated cost per year growing at these temps?

You're growing exactly what I'm growing but I'm also adding cacao, longan, lychee, black pepper, barbados cherry, noni, mangos, coffee, a bunch of heat loving fruiting trees. I figured I would be safe with night temps around 65 since it jumps during the day. My biggest concern is going to be pollination and I'm trying to develop a plan for that. The side flip up on mine and day temps can be 70's in spring but if there's an odd trend I may not open the sides. I need to learn more about adding bees, moths and other benificals for pollination and pest control. Have you done this?

Tam, I really don't keep track of the propane usage. What it is, is what it is. The propane tank for the greenhouse is a 1000 gallon tank. It gets filled the first time around September 10th. After that I have it refilled when the tank gets down to 30% full. Because of propane gas expansion inside the tank from sunlight, heat and ect. they only fill it up to 80% full each time. I get it filled perhaps 4 times during the fall, winter and early spring. So each time it is filled takes approximately 500 gallons of propane. Four refills/year equals APPROXIMATELY 2000 gallons of propane per year. Last year propane was .90 cents per gallon on average, so total cost to heat the greenhouse would be around $1,800.00 to $2,000.00 per year. Remember that Colorado winters are a lot longer and a LOT COLDER than winters in Virginia. I keep the night temperatures at 60F. for the entire winter. I think 60 would be fine for any tropicals you wish to grow. 65 would certainly be OK. Pollination I never worry about as I pollinate by hand, but mostly I pollinate with gibberillic acid sprays. Bees, moths and ect., of course are not around in Colorado during the fall and winter. No matter how cold it gets, it is VERY IMPORTANT to always leave a door or a vent cracked open as a greenhouse with a lot of plants inside, will deplete the CO2 in a hurry, and without CO2 the growth stops. Your number one asset is light. My greenhouse is at 5,440 feet elevation, so the light intensity is extremly strong. If I was going to build a new greenhouse, I would heat it with infrared heat. Infrared heat technology for greenhouse heating is a very efficient and "inexpensive" heat. You might look into heat curtins that are put in the inside roof and open in the morning and close in the evening. All of this, of course is money, money, money. Take care and LOTS OF LUCK on the new venture for a neat girl. - Millet

Thank you... as always very informative. gibberillic acid sprays??? You mean like megagro? How is that going to aid you in pollination? What about those vibrating wands they use in tomato hot houses? Have you seen those?

I thought about adding co2 but it seems that too would get expensive. My main movtivation is to keep as natural as possible. Once in my hands everything is treated organically and naturally.

I would like to design a small aquaponic system that is affordable for almost any family then teach them how to do it.

Right now I am looking for articles from people to help others grow in containers. The info is all over the place. It's all hard to follow.

I know nothing of Megagro. I purchase Gibberillic Acid (made by Abott Labs). Using gibberillic acid as a "polinizer" for citrus is actually a very old technology. People have used it for many year to set citrus blossoms. Gibberillic Acid when sprayed on a citrus bloom sets the bloom ("pollenizes"),even on self-incompatible citrus cultivars, such as Minneola, Nova, Orlando, Robinson, Sunburst and ect. The reason I like gibberillic is because it pollenizes the flowers, sets the fruit which then will mature completely seedless. I'm not much into organic culture. I don't have anything against it, per se, but I much prefer to use standard growing methods. - Millet

Hair, the lowest my gh gets in winter is 45F. I've a thermometer w/humidity, and an alarm..the main component stays in the house..if the temps dip below 45 the alarm beeps..It's important you buy something similar to the alarm I have..I learned the hard way..Aside from the gas heater, I also have an electric heater in case the gas heater goes off..Millet is 100% correct on keeping a window/screen door opened just a bit..Gas built up which caused the heater to go out on the one of the coldest winter nights..lost 37 plants, including citrus.
I also found by adding some type of container filled w/water helps not only heat but humidity, too. I started using the container, (sealest 5 gallons) 2 yrs ago, and what an improvement.
I do not use shades, or blinds..I want as much sun as possible in mid-winter. And that sun helps warm up the gh.
The important thing is getting the alarm. Believe me, it's worth every penny..Toni

Millet:

http://megagro.com/megagro_faq.htm

We've had great success with megagro. I'm spraying it also on my tropical fruit trees. I have 2 foot june plums trying to load with fruit and you should see my noni!!!!!!!!! amazing really.

Millet..Tams..I used a bottle of MegaGro in the concentrated this summer and was very happy with it. In using the concentrated you can mix it according to Growth Flowering, Propagating,
I know in the past using Gibberillic Acid was discussed here but the posting are gone from here.
As Toni mentioned in her above posting an alarm is a very good tool. The one I use is wireless and is very well worth the 40 something dallars.

Millet I also had seen Gibberillic Acid listed on the web.It would be interesting to know if you use the Water or alcohol mix, And if you use it in the PPM.. Dale

So basically you should crack a window or something? How much? How does it affect heating costs?

Hair, do you have a screen on the door? If so, you can leave that opened instead of a window..The screen in my gh is left about 3/8"..believe me, I learned the hard way..Wish I'd known this beforehand. You don't want it opened so much that it keeps your gh freezing, and wasting heat, to boot. Especially w/current gas prices..Toni

In reference to excesssive heat... what about small vented exhast fans? The greenhouse were putting up has two HUGE fans inside, plus I'll add a few small exhast vents. At least I'm hoping that will be enough. At night I don't see it being as much of a problem as daytime. Am I wrong in thinking this?

Cheers!

Oh hey got a new margarita receipe that's great. Mango juice, key lime, splash of grand mariner (sp)

Toni..How do you heat your Greenhouse? Do you keep it going through the Winter..Dale

Gas buildup should never ever be a problem inside a greenhouse, if the heaters are properly vented to the outside. I use two overhead Modine heaters, a 200,000 BTU 80% efficient (my old heater used as a backup set at 50 degrees F.) and a 250,000 BTU 90+ efficient (my first line unit set at 60 derees F.). I always leave some vents cracked open even on the coldest winter days, for CO2 entry, not because of any possible type of gas buildup. I do feel sorry for Toni's plant loss because of her greenhouse freezing up. Thats a lot of hard work down the drain. It has happened to me some years back. Dale, I purchase Gibberillic in a alcohol solution. Hairmetal, yes I suppose leting in some cold air during the winter does cause the heat bill to increase, but without CO2 all growth comes to a halt. If you have a greenhouse with tropical and subtropical plants, and you want as much growth as possible during the winter, then high heat bills are part of the package. I am presently replacing my greenhouse cover with new DOUBLE wall Lexan polycarbonate glazing. In fact, I have been replacing it from sun up to almost sun down for the last two days. Getting ready for a Colorado winter. Tam, excessive heat should be taken of by providing adequate square footage of evaporation pads. The two fans in my greenhouse can TOTALLY and completely replace all the inside greenhouse air every one minute. Good luck in VA. - Millet

Dale, I use a 10,000 BTW gas heater and a 5000 Electric heater. My heater has an oxygen senser that turns off the heater when oxygen level gets low...the gh was sealed too tight so fresh air wasn't allowed to come in to provide oxygen for combustion. Remember my gh is only an 8x12, so I don't need a bigger gas heater.
The only time I keep plants in the gh is during cold months. Everything is set outside in late spring through fall. Toni

Hello Millet!
What thickness of double-wall poly carb are you using? 8mm..10mm? 4x8 or 5x12? And if I may ask, what was the best price and source for this wonderful material? Thanks..Scott

Millet:

Do you think in my area I'd need shading or evaporative cooling, or would a strong enough ventilation fan be enough?

Our humidity is worse than our heat. Our average July high is about 84 although our hottest days reach the mid 90s typically.

I feel so lucky that I decided last Aug to build my sunroom addition VS a greenhouse. It is 16 1/2' X 18'- framed in lumber with 13 1/2' cathedral ceiling. Windows facing south & east are 5' high..& 2 (wish & had 3 now) skylites facing south. It looks like a regular room addition, but since there is no heat or AC it is considered an "enclosed porch". I have glass Fr doors going out to it from my kitchen where there was once a window to yard. If I need more heat, I just open the door a crack to let house heat go in. I also bought a really cool ceiling fan that has heater in it. The fan mode blows air down & the 'heat' mode actually shoots out heat & blows it up & around & down the windows. I also insulated the walls, ceiling & floor. I put a drain in floor which goes to gutter downspout for any water that overflows on floor which is called spreadrock (hard as concrete). I have a tv in there now & we had dinner ther lately LOL----LOVE IT. My bf put speakers on wall & hooked to my stereo. Total cost for materials was about $7,000. I bought everything on sale & did it myself (with help from friends for rafters). Outside is finished & I only have to trim windows & finish mudding the drywal. I will paint walls either high gloss or semigloss white. A friend gave me mirror panels --8"x 6' that I will use to reflect more lite. E efficient flourescent lites on timer for winter. I'm so glad I did this. All my furniture will soon go in there so I can refinish my hardwood floors. Hopefully will finish that before plants have to come in for winter.

Patty, your new sunroom sounds wonderful. Semi-gloss white and mirrors will definatly help brighten it up.
I envy you..It's so much easier stepping from one room to the next, than dragging 5 gallon containers of water, from house to gh, in mid winter.
How many plants will this room hold? Are you going to add hanging plants, too? Do you have a pic of your new room? I'd love seeing it after you finish, adding plants, furniture. Bet it's cozy sitting in a room surrounded by greenery. Toni

Patty:
I am glad that your dream came through and I am sure you'd enjoy your sun room in the future. I am happy for you.

I know we discussed my future sunroom also with you but due to sudden change of my plans I am putting my plans in back burner.

Benny

Scott, I am putting up 8-mm. Lexan double wall polycarbonate. The sheets come either 4-ft. or 6-ft wide and 20-feet long. (4x20 or 6x20). All greenhouse suppliers carry polycarbonate in 20 foot lengths. 4x8 or 5x12 must be for the construction industry. I paid $1.40/square foot. Hair, yes I think your greenhouse need evapoative cooling. When the outside temperature is 90, the greenhouse will be over 100 without evaporative cooling. - Millet

I'm still missing something here.... is you open it up, lift up the sides, have fans and shade cloth do you still need cooling?

Tam, if you can open a greenhouse that much, your inside greenhouse temperatures could be either the same as or probably a little higher than outside temperatures, but never, of course, less than outside temperatures without evaporative pads. Whether or not your greenhouse requires artificial cooling all depends on what you wish to grow. - Millet

Patty_in_Wisc ..I must say, Its sounds very nice, I also give you a lot of credit for doing it yourself with the help of a few friends..Best of Luck..Dale

Millet,

I don't know how effective evaporative cooling would be, since our humidity is so high-our dewpoints average 70 or higher on the hotter (>85F) days.

Thanks Toni, Benny & Dale. I will try to post pics later.
Toni, hanging plants aren't a thought now. I still have to finish the trim around windows & doors & drywall sanding. I have a 8' table in there (loaded w/ tools for now LOL) that I will put most plants on in south facing window.
Benny, I hope you get a permit for a 3 season sunroom,..or enclosed porch. That means it won't have heat or AC & they won't be so tough on requirements. You can always add a heater (you probably don't need it) & fans.
Winter is just around the corner so I will see how well I insulated! Good luck to all with your greenhouses this winter!
Patty

Patty, yes, please send pics when it's finished. I enjoy viewing others' plants and sunrooms. Do you grow plants other than citrus? This is the reason I mentioned hanging plants. What type of furniture are you planning on adding? Wicker or something else?
Yes, winter is soon coming. I hope you get the room finished before it hits. And you're further north than I am and I can feel the difference, though it's been humid here. Good luck and hope you finish before it gets too cold..Toni