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How hot is TOO hot for inside a greenhouse?

Kinosabe777

New member
Hey guys I built a a 20x30 hoophouse and was ready to put my babies in there until another grower warned me not to because of how hot it is going to be in there this summer. I live in Northern California where it could get up to 100 degrees. The only thing I have to defend against the weather are two industrial fans I bought . Any thoughts?
 

Limeygreen

Well-known member
Veteran
The biggest thing in a empty greenhouse being empty will be low humidity with high temperature. You may consider buying some shade cloth or slats of wood to put over the glazing to cut down on light to reduce heat when leaf area is too little to try and make a more comfortable greenhouse, 50-70% should do, better if you had both so you can go with smaller plants with 50 % then as they get bigger use the 70 % until you can get the shade completely off. I am Celsius, 40 would be too much, 28 would be great if you can get it although I have grown tomatoes, peppers and leafy greens in 40 degrees with no issues with side ventilation (passive) with no issues by pounding water to them, usually 6 litres per plant per day up to 8, broken up into 3-4 rounds about 3 hours apart. Good luck.
 
open ends and sidewalls, mount your fans up high and do what you gotta do:)
ive had highs of 117 and a low of 36 already this year.
its amazing how that 117 inside the gh doesn't seem like 117 would outside.
I find it fun how when doing an indoor if it gets less than 60 or more than 80 alarms start going off. now I just tell myself to stay calm and remember what the temps will be in 6 months in the gh
 

Jahcr1

Member
Over 34 centegrades the resin prduction is damn low... plagues usually attacks and metabolism go super slow.. put some fans to solve this
 

farmerlion

Microbial Repositories
Mentor
Veteran
Kinosabe777, mine has been 100 to 110 a couple days. I had good ventilation with fans and one side up about a foot. It was only 10 degrees hotter inside than outside. I misted the plants as often as I was around to do so. In the end they are fine and doing well. It's a lot hotter in Africa and Mexico where my genetics are from than in North Dakota. I told my plants suck it up ladies, your not getting A/C. Peace
 

OldPhart

Member
Put something like the below swamp cooler in one end, and put an exhaust vent high on the other end... problem solved. I've seen greenhouses in areas where the temp may be over 100F for two months straight; they use swamp coolers and never have any issues. The plants actually love the humidity/heat combo. I know they make swamp coolers specifically for green house use, but I can't seem to find a link to one; although I didn't look too hard.

https://www.amazon.com/Portacool-PAC2K361S-Portable-Evaporative-Capacity/dp/B000Z5CVPW
 

coldcanna

Active member
Veteran
Like they said as long as you keep the humidity jacked way up the plants do great in the high temps, after all this plant is from the equator
 

ChaosCatalunya

5.2 club is now 8.1 club...
Veteran
Aso thers said, high humidity ,swamp coolers that blow over cold water

They sell a product here in Spain that makes a thin wall of water like a door at the entrances, cools greenhouses down no end
 
I think it is somewhat strain-dependent. I'm growing Kosher Kush in a 12x7x7 portable greenhouse and the Kosher Kush took a look at the heat and laughed. Plants are so big, the top branches are bending over. I have to get some caging to support them.
 

Noonin NorCal

Active member
Veteran
I think as long as you have proper ventilation and constant air moving around you should be fine. We are running some type of Og supposed to be a fire og phenotype. The things are stretching like hell in our Solexx Greenhouse. We light dep it from 7-7. have been covering for 2 weeks now
 

OregonBorn

Active member
Cannabis is not from the equatorial zone. Cannabis is believed to originate from the Asian Steppes, north of the Himalayas to Mongolia and Southern Siberia. So it is a plant of more northern latitudes.

That said, Cannabis is an arid and heat loving plant. I have seen mine go to 115 F. no problem. The leaves are cooler than the air though. They respire water like we sweat. Water them more than normal in the heat. I like to keep my GH under 95 F., with an optimal temp of 86 F. In heat waves (over 90 F., which means over 100 F. in the GH), I put 50% shade cloth over the GH to cool it down. I also open the from door and back windows. I have never lost a pot plant to heat. Even in 110 F. heat in Gilroy, CA.
 
Cannabis is not from the equatorial zone. Cannabis is believed to originate from the Asian Steppes, north of the Himalayas to Mongolia and Southern Siberia. So it is a plant of more northern latitudes.

That said, Cannabis is an arid and heat loving plant. I have seen mine go to 115 F. no problem. The leaves are cooler than the air though. They respire water like we sweat. Water them more than normal in the heat. I like to keep my GH under 95 F., with an optimal temp of 86 F. In heat waves (over 90 F., which means over 100 F. in the GH), I put 50% shade cloth over the GH to cool it down. I also open the from door and back windows. I have never lost a pot plant to heat. Even in 110 F. heat in Gilroy, CA.

Equatorial zone would mean, more often than not, a humid zone. The tropics. I've got massive indica fan leaves in a greenhouse, just a little north of where you are (37:30 lat) and my girls are like women from R. Crumb cartoons. Big chests, big butts, big thighs. Think "Attack of the 50-foot Woman!!!"
 

OregonBorn

Active member
Equatorial zone would mean, more often than not, a humid zone. The tropics. I've got massive indica fan leaves in a greenhouse, just a little north of where you are (37:30 lat) and my girls are like women from R. Crumb cartoons. Big chests, big butts, big thighs. Think "Attack of the 50-foot Woman!!!"

Well, the steppes are humid, but hardly equatorial. Or tropical. More like the 50th parallel. I am near the 45th parallel BTW. Not in Sunny CA at the moment. Though it is sunny here this summer. Perfect weed growing weather.

I had a tightly held indica strain from Mendocino growing with 18 inch long leaves here 2 summers ago. I have photos someplace... they were HUGE. Biggest leaves I have grown or seen. They were like tobacco.

I still have a collection of underground Crumb comix that I got in Berzerkeley in the late 1970s. My 1st ex identified with Crumb's big blonde that always stomped around for some reason. Maybe because she was a big blonde? I left her in Menlo Park ;(...
 
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A

acdc

Well, the steppes are humid, but hardly equatorial. Or tropical. More like the 50th parallel. I am near the 45th parallel BTW. Not in Sunny CA at the moment. Though it is sunny here this summer. Perfect weed growing weather.

I had a tightly held indica strain from Mendocino growing with 18 inch long leaves here 2 summers ago. I have photos someplace... they were HUGE. Biggest leaves I have grown or seen. They were lie tobacco.

I still have a collection of underground Crumb comix that I got in Berzerkeley in the late 1970s. My 1st ex identified with Crumb's big blonde that always stomped around for some reason. Maybe because she was a big blonde? I left her in Menlo Park ;(...

indica strain from Mendocino would love to see those photos:tiphat:
 

St. Phatty

Active member
During the bit of heat we had this last week, it wasn't the leaves but the roots I was concerned about.

With or without a greenhouse, the soil can BAKE (depends on if you're in pots or in the ground).

I would keep an eye on the root area during the hottest parts of the day. i.e. stick your hand in there.

Long story short, my roots were water cooled this last week - 2 or 3 gallon bucket every hour or 2, in a 32 gallon pot. It would bubble a bit - and cool everything off. :woohoo:

I don't know what happens to nutrient up-take when the root mass gets above a 100 F/ 38 C ... but I think the grow process works better when they're cooler.
 

petert

Member
I e had temps at close to 100 during the day for 2 solids weeks!! That was the outside temps too!! I just went inside and hosed down the weed barrier at least twice a day.. that raised the humidity and lowered the temps.
I found some Russets ( little motherfuckers) and closed the greenhouse down and let it cook between 115-120 for 60+ minutes two days in a row in July. It messed with the plants a bit.. had probably 10% leaf die off but really did a number on the russets!!
 
I e had temps at close to 100 during the day for 2 solids weeks!! That was the outside temps too!! I just went inside and hosed down the weed barrier at least twice a day.. that raised the humidity and lowered the temps.
I found some Russets ( little motherfuckers) and closed the greenhouse down and let it cook between 115-120 for 60+ minutes two days in a row in July. It messed with the plants a bit.. had probably 10% leaf die off but really did a number on the russets!!
Did this stress cause any hermies?
 
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