# Humidity



## keithrs (Mar 9, 2012)

While I was getting ready for the SDCOS show I was thinking....(work with me here) 

Why is humidity so important? 

Than I got to thinking some more, Maybe it has to do with chlorophyll production? If a plant is loosing moisture faster than it can pull up water to the leaves then the minute pores will close to regulate the moisture loss. There for the plant lowers it Co2 intake, lowering the chlorophyll production. And if the plant leaves the pores open then too much water is lost, there for lowering chlorophyll production also.

My question to you is this an accurate theory?


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## NYEric (Mar 9, 2012)




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## Rick (Mar 9, 2012)

Actually it seems like orchids have very poor control of pores with regards to humidity. Pore control seems to be based on light (quality and quantity). Pores will be open as long as the light level is correct, regardless of the air humidity level. Most of our tropical orchids come from very high humidity systems and their physilogical mechanisms to accomodate water transport are not based on the typical temperate low humidity systems of deep effective naked rooting systems.

So orchids tend to dessicate very quickly in low humidity systems, since they are trying to pull water through both aerial roots and leaves. Keeping orchids in pots of dense potting mix generally suffocates and/or drowns orchid roots.

Seems like if humidity is down the plant just can't pull enough water up through the roots to keep up with the loss through the leaves. Causing stress that looks like wilt. We compensate by putting more water to the roots and subseqently rotting those.

Maximizing humidity was a big epiphany for my growing several years ago. Regardless of the physiological mechanisms, it cut my losses dramatically when I forced humidity to stay >70%


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## Stone (Mar 9, 2012)

Along with what Rick metioned I think its also important to distiguish between CAM orchids ( Catts Laelias Oncidium and other hard leafed epiphyites ) and non CAM orchids such as soft cane dendrobiums and paphs. CAM plants keep their stomata closed during the day so are able to withstand lower humidity at that time but its vital that a good rise in humidity occurs at night when stomata are opened for CO2. On the other hand paphs are unable to do this so must have a more constant and high humidity level. (It would be interesting to know if any of the hard leafed paphs like niveum or godefroyae are CAM).
I also agree with Rick about the mistake of compensating for low humidity by watering more. Lance burk wrote in his Paph manual about using more fans to increase humidity and while I agree with the theory of removing more water vapour from one plant to make it available to the next, in practice I failed to notice any apreciable difference in humidity levels when I introduced more fans. Maybe my air movement was already adequate?


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## Rick (Mar 9, 2012)

Plants use CAM to different degrees. Some are "obligate CAM plants", i.e. they use only CAM in photosynthesis, although they vary in the amount of CO2 they are able to store as organic acids; they are sometimes divided into "strong CAM" and "weak CAM" plants on this basis. Other plants show "inducible CAM", in which they are able to switch between using either the C3 or C4 mechanism and CAM depending on environmental conditions. Another group of plants employ "CAM-cycling", in which their stomata do not open at night; the plants instead recycle CO2 produced by respiration as well as storing some CO2 during the day.

Plants showing inducible CAM and CAM-cycling are typically found in conditions where periods of water shortage alternate with periods when water is freely available. Periodic drought – a feature of semi-arid regions – is one cause of water shortage. Plants which grow on trees or rocks (as epiphytes or lithophytes) also experience variations in water availability. Salinity, high light levels and nutrient availability are other factors which have been shown to induce CAM.

The above text suggests that CAM metabolism is not strictly on /off, but variably induced under certain conditions besides arid conditions.


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## Rick (Mar 9, 2012)

Another thing to consider is when even an arid/ CAM orchid opens pores at night, its going to getting much higher than 20-30% humidity in its natural environment.

I know that in my house with AC in summer and electric heat/dry north winds in winter, that humidity is always pretty low 24 hours a day.


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## Orchidnut57 (Mar 10, 2012)

Excellent
Thanks for this informative post


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## Lycaste53 (Mar 10, 2012)

I don´t understand anything about cellular metabolism, either what concerns my body or what concerns my orchids. What I believe (not know) is, that there is an equilibre of more than one concern, if we want to succeed in orchid culture. Humidity is one of them. But there are too: Wind (air movement), light, temperature, potting material, disease-control, fertilizer ect.
It depends on the equilibre and summary of all circumstances, for me, it makes no sens to discuss only CAM. 
I keep "obligate CAM plants", "strong CAM plants", "weak CAM" plants, "CAM-cycling plants" and "non CAM plants" all together.
They like it.


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## Stone (Mar 11, 2012)

[QUOTE said:


> I keep "obligate CAM plants", "strong CAM plants", "weak CAM" plants, "CAM-cycling plants" and "non CAM plants" all together.
> They like it.



So do I but in the past couple of years I have tried to make sure that CAM plants especially those on cork get a drink and a good mist after sunset especially in summer when they dry out in a short time during the day, and with good results. (improvement)
As for discussing only CAM, I think we have probably been through every imaginable topic in various threads and even after only a year or so for me, it seems obvious that we must revisit similar topics in an endless cycle but perhaps adding a little more up to date information or hearing some other point of view each time we do.


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## keithrs (Mar 12, 2012)

Stone said:


> So do I but in the past couple of years I have tried to make sure that CAM plants especially those on cork get a drink and a good mist after sunset especially in summer when they dry out in a short time during the day, and with good results. (improvement)
> As for discussing only CAM, I think we have probably been through every imaginable topic in various threads and even after only a year or so for me, it seems obvious that we must revisit similar topics in an endless cycle but perhaps adding a little more up to date information or hearing some other point of view each time we do.



I also water at sunset but more so because the sun(heat) doesn't dry my mounts out soooo fast.... If I water in the morning my mounts will be dry in an hour. Even still they'll be dry by morning.

I agree Stone.... We do need refresher courses.... As the case with my MSU episode that Dot had to correct me on...LOL

So, My question was not really answered.... Does humidity effect chlorophyll production?


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## abax (Mar 12, 2012)

While on the subject of humidity, I've just had another humidifier die on me...a Holmes. That's three I've used up in about five years. Anyone have any suggestions on better, larger humidifiers that hold at least six gallons?
I've been looking at an Essick...any experience around here?????


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## Rick (Mar 12, 2012)

keithrs said:


> I also water at sunset but more so because the sun(heat) doesn't dry my mounts out soooo fast.... If I water in the morning my mounts will be dry in an hour. Even still they'll be dry by morning.
> 
> I agree Stone.... We do need refresher courses.... As the case with my MSU episode that Dot had to correct me on...LOL
> 
> So, My question was not really answered.... Does humidity effect chlorophyll production?



Even in the case of CAM plants pore opening is not based on humidity. But the uptake of CO2/water for plant metabolism functions can be based on humidity since it will effect the nature of gas exchange when the pores are open.

CO2 has a much higher affinity to combine with water than O2. This is something that divers and aquarium people generally are aware of. So when pores are open they can absorb CO2 more effectively in water vapor. When the air is very dry I would guess water will be drawn out of the plant making it hard to uptake CO2.


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## NYEric (Mar 12, 2012)

I water (spray) plants with aerial roots every morning. I try to water at night because naturally that is when the temps drop and relative humidity goes up. I was taught that plants grow at night; "chlorophyll production?", IDK!


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## Justin (Mar 12, 2012)

abax said:


> While on the subject of humidity, I've just had another humidifier die on me...a Holmes. That's three I've used up in about five years. Anyone have any suggestions on better, larger humidifiers that hold at least six gallons?
> I've been looking at an Essick...any experience around here?????



I had an Essick whole-house humidifier that i really liked (model MA1201); However it died at the beginning of its 3rd season. It was quite noisy but it did a great job. It was made in USA too...too bad it died.

Definitely stay away from Hunters...i had two and both died after only one season each. 

I see humidifiers as just part of cost for orchid growing...like media or lamps. They only last a couple years so I just factor replacement into my general cost of growing. That being said, for next year I am going to try a Kenmore whole-house humidifier and see if that lasts for any longer.


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## abax (Mar 13, 2012)

I see humidifiers as cost for growing too, but I'd like one that lasts a bit more than two years. Hunters are terrible and Holmes are only slightly better. I'm considering an Essick 821-000, but I'd love to find one with a filter that can be cleaned and reused. I'll research the Kenmore to
ascertain if that product might be a bit better.

In passing, I put a small fountain in my gh mostly because I like the sound of the water...quite soothing...
it's pretty too. I'm amazed at just how much water evaporates from the fountain and it's very compact and
sits up against the wall rather neatly. Since my gh is my
sanctum sanctorum, the fountain is very niiiice.


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## keithrs (Mar 13, 2012)

Why where on the topic of humidity and humidifiers... Has anyone tried to mix a fertilizer in with there resevoir water?


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## Rick (Mar 13, 2012)

keithrs said:


> Why where on the topic of humidity and humidifiers... Has anyone tried to mix a fertilizer in with there resevoir water?



My reservoir tanks get plagued with algae and bacteria slimes without nutrient addition. If you add even a drop of fert to a humidity sump it will turn the pads and tank walls into a big, stinking, clogged up mess of bluegreen algae in no time.


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## cnycharles (Mar 13, 2012)

keithrs said:


> Why where on the topic of humidity and humidifiers... Has anyone tried to mix a fertilizer in with there resevoir water?



at least the ultrasonic humidifiers state that you should add no chemicals to the water; maybe if you had an 'impact' type impeller humidifier, but I would strongly suggest to anyone that they not breathe in fertilizer mist. bags of fertilizer don't have poison control messages except I was told for florida maybe, but what is in fertilizer isn't generally good for lungs, either as dry dust or wet mist

to try and answer your original question, I'm not aware of a situation where chlorophyll production turns off or on because of certain levels of humidity. I think it's more like the situation where any chemical processes in a cell are limited, if the basic needs of the cell aren't met. it's a wide and strange world, so i'm sure somewhere there must be a plant whose chlorophyll activity has an on/off trigger with certain humidity levels


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## keithrs (Mar 13, 2012)

cnycharles said:


> at least the ultrasonic humidifiers state that you should add no chemicals to the water; maybe if you had an 'impact' type impeller humidifier, but I would strongly suggest to anyone that they not breathe in fertilizer mist. bags of fertilizer don't have poison control messages except I was told for florida maybe, but what is in fertilizer isn't generally good for lungs, either as dry dust or wet mist
> 
> to try and answer your original question, I'm not aware of a situation where chlorophyll production turns off or on because of certain levels of humidity. I think it's more like the situation where any chemical processes in a cell are limited, if the basic needs of the cell aren't met. it's a wide and strange world, so i'm sure somewhere there must be a plant whose chlorophyll activity has an on/off trigger with certain humidity levels



Good point on the humidifier mist.... 

I'm guessing that if to can keep more water in the leaves you'll have better chlorophyll production?


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## Rick (Mar 13, 2012)

I've gone from misters to foggers to swamp cooler/wet pad.

Actually at this time my wet pad does the bulk of the humidification and the fogger covers the boost needed for exceptionally dry air.

Same for cooling.

I specially designed my wet pad so I can recirculate the GH air through it in the winter. Most GH designs aren't set up to use the wet pad in the winter as they are open to the outside air and depend on air being pulled through the entire lenght of the GH by fans mounted at the opposite end from the wet pad.

The humidification/opperation/maintenance potential of a wet pad is superior to a fogger IMHO.


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## Stone (Mar 13, 2012)

I bought a second hand evap. cooler and mounted it on the outside to blast cool moist air into the green house. It cost me 200 bucks and I've changed the motor once. Good value compared to going for a new one I think. These are everywere here. In fact I got three for that price but 2 without motors. Think they came from an old supermarket? That old steel ladder--circa 1960's.


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## Rick (Mar 13, 2012)

That would be a good deal.

I designed and built my swamp (evaporative) cooler myself. The premise is easy and cheap.

The "glaciercore" blocks were the hardest thing to find, but they were readily available at one of the bigger GH supply. The rest is just rain gutter, a big fountain pump, a stock tank, garden hose, a drilled up piece of 1/2" pvc pipe for a spray bar, and various brackets/bracing.

I mounted 4 cheap "weathershield" box fans across the front to pull the air through the wet blocks.

I think all together I spent about $200 for a 8X2 wet pad system


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## Stone (Mar 13, 2012)

Are your fans blowing or drawing the air from the other side? What horsepower?


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## Rick (Mar 13, 2012)

Stone said:


> Are your fans blowing or drawing the air from the other side? What horsepower?



They are drawing air from the other side.

Don't know the hp right now, but these are small 20" window box fans.

I also built a shroud with louvers in it that sits on the outside wall that the wet pad sits on. During the winter the louvers are down to block outside air from going through the pad, but recirculate the internal air in the GH. During summer when I want more cooling effect (with humidification) I pull the louvers up to block the recirc and bring in outside air.

There is also a 1/4 horse ventilator fan near the GH peak set for about 90F. If the wet pad and foggers can't cut it, it comes on and really pulls the air through the wet pad.


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## NYEric (Mar 14, 2012)

If this summer is a relatively warm as the winter has been here I will probably look into adding humidity by replacing my 10-jet ultrasonic fogger and using the AC.


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## Rick (Mar 14, 2012)

NYEric said:


> If this summer is a relatively warm as the winter has been here I will probably look into adding humidity by replacing my 10-jet ultrasonic fogger and using the AC.




What's the humidity like in your appartment Eric?

That sounds wild to keep things up that high around furniture and stuff.


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## jtrmd (Mar 14, 2012)

Rick said:


> What's the humidity like in your appartment Eric?
> 
> That sounds wild to keep things up that high around furniture and stuff.



I was getting ready to say the same thing.


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## jtrmd (Mar 14, 2012)

Rick said:


> That would be a good deal.
> 
> I designed and built my swamp (evaporative) cooler myself. The premise is easy and cheap.
> 
> ...




I built my own wet wall in my old hobby size greenhouse the same way.I got the pads from Grainger,pump from Harbor Freight,and everything else from Home depot.I think all together it was like 150-200 bucks to build a 4 x 4 wet wall.I had an exhaust fan(if I remember correctly it was one of those attic fans) towards the top of the GH that pulled the air through it.


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## Justin (Mar 14, 2012)

With indoor orchid growing, you have to balance the well-being of the plants with well-being of the house structure. 

If i can keep indoor humidity around 40-50% in the winter find that enough to keep plants happy.

I'm sure they would prefer 70% but it would destroy the house. In fact this winter i didn't even run a humidifier after the unit died. 

I just accept I don't grow in a greenhouse and plant growth is slower than it could be but it is good enough for indoors. My roths and other multifloral paphs still grow like weeds and bloom regularly. 

Actually, in central ohio, summers can be extremely humid. Even with indoor air conditioning there are days when indoor humidity is close to 70%. Mold can be a major problem for a lot of older homes in this area.


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## keithrs (Mar 14, 2012)

Justin said:


> Actually, in central ohio, summers can be extremely humid. Even with indoor air conditioning there are days when indoor humidity is close to 70%. Mold can be a major problem for a lot of older homes in this area.



No kidding.... I past through that area last summer on my way to NJ and I about died.... 90 deg with 90+% humidity. God how I missed Cali!!!!!!


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## NYEric (Mar 14, 2012)

Rick said:


> What's the humidity like in your appartment Eric?
> 
> That sounds wild to keep things up that high around furniture and stuff.



Humidity is very low but we spray plants with aerial roots every day and water every other day.


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## cnycharles (Mar 14, 2012)

I tried twice to use humidifiers in the winter on a regular basis, and the first time years ago one of the old padded chairs the old landlord gave me sprouted stuff and mildew started up around the outside edges of the ceiling (was winter and very cold spots). I was using an old centrifugal humidifier and didn't realize how much moisture it was putting out. Now in the basement of the new place where my apartment is, when I finally get my plant cart put back together, it won't matter how much humidity I have inside the cart, as the basement is huge and the boilers put out dry heat


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## Rick (Mar 14, 2012)

cnycharles said:


> I tried twice to use humidifiers in the winter on a regular basis, and the first time years ago one of the old padded chairs the old landlord gave me sprouted stuff and mildew started up around the outside edges of the ceiling (was winter and very cold spots). I was using an old centrifugal humidifier and didn't realize how much moisture it was putting out. Now in the basement of the new place where my apartment is, when I finally get my plant cart put back together, it won't matter how much humidity I have inside the cart, as the basement is huge and the boilers put out dry heat



Eric's place is way too out of control at this point, but you could do some cheap and easy enclosures around plant racks with clear shower curtains and contain some of that humidity.


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## NYEric (Mar 15, 2012)

Rick said:


> Eric's place is way too out of control at this point,



What does this mean!? :viking:


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## eggshells (Mar 15, 2012)

If you have a manageable size collection. You can purchase something like this. the plants themselves maintain the humidity inside when its close 70-80% rh. I bought two of them 4 tier ones for $30 ea.


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## Rick (Mar 15, 2012)

NYEric said:


> What does this mean!? :viking:



From your "Miscelaneous..." thread you should be able to answer that one yourself Ericoke:oke:

Of coarse I don't mean it in any derogatory sense, but as a praise of your extreme orchid adict status:wink:


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## hchan (Mar 15, 2012)

eggshells said:


> If you have a manageable size collection. You can purchase something like this. the plants themselves maintain the humidity inside when its close 70-80% rh. I bought two of them 4 tier ones for $30 ea.



Those are good, but don't forget you might need a fan for air circulation


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## Clark (Mar 15, 2012)

eggshells said:


> If you have a manageable size collection. You can purchase something like this. the plants themselves maintain the humidity inside when its close 70-80% rh. I bought two of them 4 tier ones for $30 ea.



Mine came with casters, and rolls through the sliding glass door easily.
Handy for the windowsill grower.


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## NYEric (Mar 15, 2012)

Rick said:


> From your "Miscelaneous..." thread you should be able to answer that one yourself Ericoke:oke:
> 
> Of coarse I don't mean it in any derogatory sense, but as a praise of your extreme orchid adict status:wink:




:wink: 
Oh, OK, thanks.


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## Stone (Mar 16, 2012)

eggshells said:


> If you have a manageable size collection. You can purchase something like this. the plants themselves maintain the humidity inside when its close 70-80% rh. I bought two of them 4 tier ones for $30 ea.



I want to get one of these to put inside my g/house for keeping certain things a touch warmer over winter. Is there a small heater anyone can suggest?


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## eggshells (Mar 16, 2012)

Stone said:


> I want to get one of these to put inside my g/house for keeping certain things a touch warmer over winter. Is there a small heater anyone can suggest?



Yes but not a heater. Those seedling mats will be good enough.


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## Ray (Mar 16, 2012)

I sell a TON of those Hydrofarm mats. They fit perfectly into a standard nursery tray (I have windowsill versions, too), and even though the instructions say not the submerge them, I had one stay underwater all last summer, and when I plugged it in, it worked like a charm.

They only consume 17W, so won't kill your utility bills.

I originally started using them to get plants established in S/H pots faster, and found that it worked so well, I outfitted a bench in the GH with a larger mat, and now it's my standard practice for all plants.


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## Stone (Mar 17, 2012)

Ray said:


> I sell a TON of those Hydrofarm mats. They fit perfectly into a standard nursery tray (I have windowsill versions, too), and even though the instructions say not the submerge them, I had one stay underwater all last summer, and when I plugged it in, it worked like a charm.
> 
> They only consume 17W, so won't kill your utility bills.
> 
> I originally started using them to get plants established in S/H pots faster, and found that it worked so well, I outfitted a bench in the GH with a larger mat, and now it's my standard practice for all plants.



I would like to keep the temp. inside the tent about 20c when outside would be 16c. Do you think that would be enough to raise the temp 4c?


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## eggshells (Mar 17, 2012)

I think so I just have two t5 inside and it's always 5-6 degrees higher than the outside.


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## Ray (Mar 17, 2012)

They are designed to raise the root zone temperature about 5°-8°C above ambient by making direct contact. I really don't know what impact they have in open air.

FWIW, I have a 55-gallon fish tank in my unheated basement (about 15°C over the winter), containing two of those, covered with sphagnum, as my nursery for seedlings. The temperature in the tank is 23°-25°C, but it also has a single, 54W four-foot T5 fixture on top, separated from the tank by a 2mm thick piece of clear acrylic, so I don't know how much contribution it is making to the heating..


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## Ozpaph (Mar 18, 2012)

Raising the temperature of a large volume of air 4C takes a lot of energy. A heating mat wont do it.
I've used the mats in a aquarium/ seedling tank setup and they work well. I put the mat UNDER the aquarium and 2cm water in the tank so its gently heated (also raises the humidity). Just raise the seedling trays in the tank above the water.


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## keithrs (Mar 18, 2012)

I have a shelf about the size of that tent that's enclosed. I have no heater in it and my min temps are about 5-10 f higher then my house at night, in fact I have to open it up at night to get it cool after a semi warm day. Couple floresent light is all you would need to warm it during the day. Add some water trays and the heat will still constant through the night if sealed good. If you don't want/need light in it them a small space heater will work fine.


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