Lies our fathers told us humidity

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Moses249

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So I been growing for a long time and am starting to feel like i was lied to about humidity and cannabis especially during flowering. I have always tried to based on the litreature in books and online to keep the humidity in my flower room at 50- 55% day and night. However I am seriously beginning to suspect that actually cannabis likes much higher humidity when flowering like upwards of 70%. I have also followed some grow diaries on here by people that really seem to know what the fuck they are doing like gettogro and have seen that they are actually buying and installing large scale humidifiers in order to get the humidity in thier flower rooms up higher than what the litreature says. so what the fuck is the deal? I mean for real? why has all the litreature and online posts telling people to keep thier humidity down when that is really hurting the plants? So farmers tell me what u think and what you do and why you think and do what you do. Lets hear from some people that arent just vomiting back up jorge's books.
 
eastcoastseeds

eastcoastseeds

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well higher humidity will cause bud mold in denser strains. if ur growing str8 sativa u can have humidity up tht high. but i wouldnt imagine anybody wanting their rooms hittin 70 percent wen they have chuncky buds on em. i keep mine under 50 %
 
GanjaAL

GanjaAL

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The word around here is 65% early flowering... then reducing it at the middle and then down to about 50% in late flower. Just what most of the growers on here have stated they are doing. Also I would think CO2 would have some part to play with how high and how low you go as well.
 
altitudefarmer

altitudefarmer

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70% @ 70° F for the win. I diffuse a blend of rosemary, lemon, eucalyptus, clove, and cinnamon oils to kill all airborne pathogens. Never seen botryitis or any other mold since I've used the essential oils. PM does not depend on humidity to manifest, it prefers big temperature fluctuations.
Google "VPD" for some fun reading, or find the thread her on the farm.
I've had excellent consistent results since I became aware of vapor pressure deficit in my grows.
 
ttystikk

ttystikk

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I run 70%+ humidity through most of flower- including to the end recently, and my plants look none the worse for it. I've always tried to keep my humidity up from veg through mid bloom; the higher I got it, the better my girls liked it, up to about 75%.

This is especially important for co2 supplementation, as low humidity actively interferes with the plants' ability to take up the gas. Raising temps into the low 80s helps by speeding up plant metabolism, but again one has to mind their RH closely, so that it stays up near 70%.

People are buying big humidifiers to counteract the effects of their huge AC units' tendency to dry the air out. What these guys are doing is very wasteful from a power usage standpoint; after all, they are paying to remove that humidity- and they'll pay to remove what they're adding!

Using a chiller and air/water heat exchangers greatly reduces the loss of moisture- this is just one of the many ways water chilling can save you money!
 
LexLuthor

LexLuthor

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I have been running RH around 60-65% and temps around 75F during flower. The people at CC say to drop the RH over time during flower all the way down to 20% in the final week, but thats when using there UC system. Something about causing drought-like conditions to increase resin production, but since the roots are constantly in water it doesn't actually cause the plant to dehydrate, or something like that.

I think that would also work for rockwool, coco, and other substrate if they are watered multiple times a day. I know VPD shows plants should have higher RH as temps get warmer, but low RH during the final week or 2 of flower helps resin production.

I really wish there were more University studies on cannabis lol.
 
sixstring

sixstring

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can you point me to the thread on vpd,im interested in reading it.i run my rooms at 30-35% with no problems but i keep my roots happy and my temps in check.
 
LexLuthor

LexLuthor

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can you point me to the thread on vpd,im interested in reading it.i run my rooms at 30-35% with no problems but i keep my roots happy and my temps in check.


If you dialed-in your nutrient regiment with RH in the 60-70% range, you'd probably get quicker growth. You won't see deficiencies just because the RH is low, especially if your nutrients are dialed-in, but with RH in the 30's, it does restrict co2 uptake.

Use the search function to find the thread, your try a Google search, I'm not sure what section it would be in.
 
M

Moses249

99
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70% @ 70° F for the win. I diffuse a blend of rosemary, lemon, eucalyptus, clove, and cinnamon oils to kill all airborne pathogens. Never seen botryitis or any other mold since I've used the essential oils. PM does not depend on humidity to manifest, it prefers big temperature fluctuations.
Google "VPD" for some fun reading, or find the thread her on the farm.
I've had excellent consistent results since I became aware of vapor pressure deficit in my grows.
if your day time temps are 70F what are you doing for night time temps? staying the same or going down to 65?
I run 70%+ humidity through most of flower- including to the end recently, and my plants look none the worse for it. I've always tried to keep my humidity up from veg through mid bloom; the higher I got it, the better my girls liked it, up to about 75%.

This is especially important for co2 supplementation, as low humidity actively interferes with the plants' ability to take up the gas. Raising temps into the low 80s helps by speeding up plant metabolism, but again one has to mind their RH closely, so that it stays up near 70%.

People are buying big humidifiers to counteract the effects of their huge AC units' tendency to dry the air out. What these guys are doing is very wasteful from a power usage standpoint; after all, they are paying to remove that humidity- and they'll pay to remove what they're adding!

Using a chiller and air/water heat exchangers greatly reduces the loss of moisture- this is just one of the many ways water chilling can save you money!

Are you running 70% humidity during the day and night? Or do you have different settings for day and night? I dont know but it seems like maybe its a good idea to run it slighlty drier during the dark period to help the plants respirate or something?

R you guys running the same during the day and night for humidity?

Thanks to all for the respones, I just find it incredible that all the books + magazines + most conventional regurgatated humidity threads online all the say the same shit about 50% humidity during the day and night which is cleary total fucking bullshit.
 
sixstring

sixstring

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313
i run 78f & 30% rh lights on and 65f & 35%rh at night and im pretty sure my plants r getting plenty of co2.i think it comes down to what they get used to,what they were germed and vegged in as well.heres a pic just to show co2 intake lol
Bh 041
 
LexLuthor

LexLuthor

2,972
263
i run 78f & 30% rh lights on and 65f & 35%rh at night and im pretty sure my plants r getting plenty of co2.i think it comes down to what they get used to,what they were germed and vegged in as well.heres a pic just to show co2 intake lol
View attachment 306072



I meant in no way that you couldn't grow buds. But low RH will cause stomata's to close, not completely closed, but enough to restrict some co2. Thats all I was saying.
 
sixstring

sixstring

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If you're running your rh below 60%, I guarantee your girls are leaving co2 on the table.
but im not putting any co2 on the table ;) during hot summer months i will shut off my intakes and switch to sealed with a/c but then running bottled co2 naturally brings rh up around 55-60% towards the end on the cycle.the bud in that pic is 46g and leaning on a 16 oz solo cup,im pretty sure i would have mold problems with that strain if i ran 70% for most of flower.i would say new growers should aim for 40-50% at all times with or without co2 even though the topic was not about co2. and more experienced growers could benefit from slightly higher numbers.the article from maximum yield is good,but are they talking about pot or lettuce?thats one reason i take anything from that mag with a grain of salt,but i do read it.
 
sixstring

sixstring

7,079
313
Yes, I've had it. It showed up as a result of big swings in temp and humidity between day and night.
nice ,you have 2 screen names ? are you sure it was temp swings.what makes the powdery mildew spores bloom and what do they feed on,temps or humidity?i ask because the ONLY time i ever saw it in my room was with rh over 65% never mattered what the temps were cause they have been all over since i first started growing indoors.one of my buddies runs @ 72f day and night and has several major pm outbreaks. i recommended a complete shutdown and bleached floors,walls,ceilings,clean all equip and start over from seed.well he got it agin as soon as he started flower ,as his rh climbed to 65-70% when the plants got big.so now i let him run my sulfer burner a few times and he runs a dehumidifiyer @45% and no more problems going on 6 months.
 

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