Humidity Question? What's too high during flowering?

Hey everyone, I have a question that I kinda know the answer to but want to see what the limits are. I have a room built outside and where I'm at has high RH to begin with. So during veg RH was around 65-80 and now it's in flowering and is around 60-70 with a little higher temps still sitting around 77-81 for another couple of weeks. I know the RH should be around 40-50 during flowering, so I've read everywhere, but I would like to know what the limits are. Q. Can I get away with the higher RH levels or will it severely hinder my yield or worse ruin the buds? They actually look really good, maybe a lil small but look real nice so far. I don't have pics on hand, but I will try to post if anyone actually wants to see em. Thanks for any insight.





4ThePeople

I'm no expert but willing to contribute my anecdotal experience. I had relatively loose / non-dense buds get molded before the plant was even finished at RH in the mid 50's to mid 60's range.Temps in 70s-80s. Growing DWC and sativa strain. Was only a relatively minor portion of the yield, but just to give you a data point. Some strains probably more resistant than others, other environmental factors, etc, but for me personally, now that I also live in a place with relatively high RH and wanting dense buds, I am definitely investing in a dehumidifier before I flower any plants.

I agree with that. You should really be shooting for an RH < 50%, and temps above 70. Bud rot will start to happen with that high humidity and low temps. you need to get that RH down brother. Do you run your grow lights during the nighttime?

also, the lower RH during flowering will make for some super sticky buds. High humidity is the devil's work.

If you have to flower in RH above 60%, you may want to take some preventative measures to avoid mold. I use a product called Actinovate which is a streptomyces strain that attacks mold spores. I thiink you could also look into using a diluted Hydrogen Peroxide spray to take out spores before they pop. Maybe others have more ideas on preventative measures?

Awesome info guys !..

So is there any bad side affects on having low humidity?

Messi BudGrower

Ok,Thank you for the responses. I am growing white widow, cream caramel and northern lights, my grow room is approx 8x4x7, I have an 16" oscillating fan on them and an 6" out and in, but I tend to keep the door open a lot of the time to keep temps down cause it's still not enough yet since where I live is usually fuckin hot and humid,but temps will be comin down soon, so will RH,but till then. I am growing in FFOF with 20% or so perlite, I include hydrogen peroxide in the water but have not sprayed with it, if that helps at all. Also, I switched my lights recently, I am currently running them on during the day and some night. I was adjusting for temp swings we had recently but has seemed to go back to hot, so they tend to stay around 79-81 deg with lights on and 72-77 deg with lights off. If the temps stay around 81 can the RH stay a little higher? I'm thinking just another couple weeks, or do I need to invest in some way to get it down right away? Thanks again for the responses and help.





4ThePeople

messibudgrower said:

Awesome info guys !..

So is there any bad side affects on having low humidity?

Messi BudGrower

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You'll get different opinions on that question. I don't have any scientific studies to point to but I'll take low humidity over high humidity most of the time. If cloning I will dome a plant for a bit, but otherwise I grow in the dry Colorado air and have no real problems. RH will always go up when I water and once my plants are in the greenhouse, it varies with the weather conditions but mostly stays low (20% or lower RH common).

I have seen ideal RH levels for each phase of growth mentioned on this forum but I don't know what studies these numbers are pulled from. I just know I have LOTS of problems to deal with if humidity is too high (like above 50%) during seedling or flowering stages.

Good because my RT Is 82-85... with RH 20% -25%


Thanks for the info bro !
Messi BudGrower

Up your air circulation if your RH is too high and you cant get it lower. This will atleast help your plants keep stagnant moist air away from their leaves.

I use greencure, its potassium bicarbonate and is labeled for organic use.

FreeLivin said:

Hey everyone, I have a question that I kinda know the answer to but want to see what the limits are. I have a room built outside and where I'm at has high RH to begin with. So during veg RH was around 65-80 and now it's in flowering and is around 60-70. Thanks for any insight.
4ThePeople

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I'd like to ask where is your gauge reading the Temp/RH ???
Base of plant?
Top of Canopy?
Area between lights and Canopy?
At lights?

All these spots will yield different readings....
You need to check what the Temp/RH is at the canopy/cola top...
This area, will run 5-9 degrees hotter, and RH will be 5-12 points lower....

This area, is where your giant buds spend the most time... what's it running there....

Sand4x105 said:

I'd like to ask where is your gauge reading the Temp/RH ???
Base of plant?
Top of Canopy?
Area between lights and Canopy?
At lights?

All these spots will yield different readings....
You need to check what the Temp/RH is at the canopy/cola top...
This area, will run 5-9 degrees hotter, and RH will be 5-12 points lower....

This area, is where your giant buds spend the most time... what's it running there....

Click to expand...

Hey, Sand4x105, I placed it right atop the bud site, it's a little hot this evening apparently but is supposed to get down to mid 60's tonight. It is currently reading RH 45 and Temp 86, it usually doesn't get higher than 82, but the door had been relatively closed this evening, I'm looking at getting LEDs to replace what I got to help with temps. attached are a couple of pics from this evening, the one in the rear is a northern light, the stunted one on the right is a cream caramel and the stunted one on the left is white widow, they're autos though, I know most of you here done like autos, oh well, that's what they are this time.. They are just over 6 weeks, Day 46 Thanks Again.



4ThePeople

Except for your issues( looks a lil stresses)plants look pretty nice for autos. Got to get your humidity under control tho. Don't want your hard work to mold.

Sent from my SCH-I545

Thank you Alwaysgreen420, I think I stunted two of them but the CC is producing some nice buds, I kinda did a lil lst on her, just a little and the WW is just small at about 20", but the NL is 37" and just starting to bud, hopefully she'll produce a decent amount.

The RH has been steady between 37-45 and temps between 72-78, hopefully the weather here will stay a lil cooler and I can maintain these readings. I do keep fans on them, but I'm going to purchase a dehumidifier before summer comes back around. Thanks for the advice everyone.




4ThePeople

humidity level of about 50% to 60% is good until the last 2 weeks of the flowering time. some growers keep it around 40% to 50%

It's always "something"...... I personally do not worry about humidity unless water is forming where plant material over laps. At which point, I increase fan speed and put the lights a lit closer to the plants, it increases the temp at the bud site and air flow helps dry and keep from overheating. Good luck.

Hey Weedow, Ben, thanks. Seems my Rh will be under control for a lil while since temps are dropping, since I'm growing outdoors technically I get outdoor weather, so my temps had been kinda high when my RH was higher as well, with fans on them, so hopefully that kinda balanced it out, I hadn't been worried during veg but kinda was this far into flowering. Thanks again



4ThePeople

I'm surprised nobody's point out the fact that your killing your microbes by adding hydrogen peroxide to feed water.
also relative humidity can be higher during the flowering phase. Mold is apparent in stagnant improperly ventilated and uncirculated rooms. Mold will not colonize in a high current room regardless of relative humidity.

tikitoker said:

I'm surprised nobody's point out the fact that your killing your microbes by adding hydrogen peroxide to feed water.
also relative humidity can be higher during the flowering phase. Mold is apparent in stagnant improperly ventilated and uncirculated rooms. Mold will not colonize in a high current room regardless of relative humidity.

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Hey Tikitoker, thanks for the response. I hadn't noticed any signs of mold, prob cause I do have higher temps and fans on them, but I wanted to be on the safe side.
As for the hydrogen peroxide, I had read in a few diff places that a little bit is very beneficial for numerous reason but hadn't read about possible problems. I use about two full caps in 2L bottles, about a half gallon, would you mind going a little more into detail about the potential cons and whether you think the little amount I use is still too much. I couldn't find the posts I read from awhile ago but found one that kinda discusses pros. http://forum.grasscity.com/advanced-growing-techniques/707074-using-hydrogen-peroxide-treat-prevent-root-rot.html Well, thanks again. I appreciate any advise and or insight.



4ThePeople

Sure. H202 is good when Hydro and sterility is key. Its an oxidant and de chlorinate water, sterilize equipment and air stones. Its very effective when used in modest amounts. If used in soil it will kill all microbial activity after a few applications. and once broken down (usually within 12hrs) separates into hydrogen and oxygen supplying an increase in dissolved oxygen and that a boost for the roots. It effectively oxidizes pathogens and cleanses the root tissue and allows once suffocating roots to once again breathe and assimilate nutrition.

Hey Tiki, thanks for the reply. So do you think I should cut out the little bit of HP? What are some of the significant downfalls to losing the microbial activity? Sorry if they're stupid questions, I had just gone based off what a few others recommended on another site and a few articles I've read. But I don't want to cause any problems for myself, I haven't had an issue with root rot or anything, just opted to use that technique. Thanks again.



4ThePeople