Light and oscillating fans advice.

Star Dog

Star Dog

Well-Known Member
Hi chaps this is my 1st post on riu I need some advice regarding direct light temps and if I should have the fan blowing lightly over/on the plants or only circulating the air in the tent?

I had the fan oscillating over the plants very lightly but a couple of plants have a few leaf edges turning up, I've lifted the fan above the light for the time being, I've also bought a speed controller for it any, advice welcome?

The air temp is fine at 25c but under the light (600w) the direct light temp is 28c.

So what is an acceptable direct light temp and should the fan only be circulating air or actually blowing lightly through/over the plants so they move slightly as the fans passing ?

Thanks Sd
 
Star Dog

Star Dog

Well-Known Member
I'm wondering if anyone can see this? Members have been helpful but I've been asking questions on other people's posts, anyways...
I've since taken the temps from the leaf with an infrared thermometer 22.5/23c, and I've moved the fan up to the top of the tent imo it was blowing a little hard for my liking, in the past years I've always used a small fan but I'm noticing a little wind burn this time?
Anyway moving it up and facing it so it's deflecting of the roof coupled with a plug in dimmer has them just lightly moving/fluttering.
Screenshot_20200829-111522.png
The fan is on that pole fixed by a L bracket and cable tie, that makes it easy to adjust.
_20200829_112442.JPG
I've just got back after years away from it, it's surprising how quickly you forget the important details, example I had to google the h202 + nitrozyme ratio :oops:
So I've planted a pack of sensi blackberry, some of the plants look great other have a touch of tip burn, one looks under fed and 2 look excessively dark is it normal, i don't mean they look bad but they aren't as uniform as I expected, it's been a long time since I started from seed it might be the norm I really don't know?

Cheers SD
 
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jondamon

jondamon

Well-Known Member
Hello.
What replies are you looking for?

Temps should not be in direct light as using HPS you also get radiant heat when gauges are placed In direct light.

Other than that everything you’re doing sounds good.

keep your temps between 20-25C when your gauges are not in direct lamp light.

keep your Humidity between 40-65% and you shouldnt see any issues.

there will be people that tell you to work your room variables based on VPD vapour pressure deficit.

to me this is just another set of variables to try and control and you can get too hung up on VPD charts and not actually reading your plants
 
TropiKanna

TropiKanna

Well-Known Member
I have multiple fans in my tent... 2 vivosun tent clip fans... one blowing directly at my lights and one on the opposite side circulating air around my canopy. Then I have a 4 inch inline with controller set at the bottom on low to take in fresh air and i have a filter and fan to exhaust hot air at the top of my tent... hope that helps
 
Renfro

Renfro

Well-Known Member
Most of my grow is sans tent, that said I setup a tent in my veg room so I could test strains and such without messing with production.

I do not have a fan in the tent. Couldn't figure out where I would put it without it blowing directly on plants or just eating up space. I use a pretty strong exhaust fan and two sets of high CFM poles. Hot air out the top and cool air in the bottom (passive intakes). I can see the leaves moving from the resulting airflow in the tent. I figure thats good enough and have never had any issues.
 
Star Dog

Star Dog

Well-Known Member
Ah thanks Renfro you've started a torrent of replies :-)

I've only had windburn once in the past when I had a fan blowing up through the canopy, but there's a couple of signs of it in the two corner plants.

SD
 
jondamon

jondamon

Well-Known Member
Star Dog said:
Ah thanks Renfro you've started a torrent of replies :-)

I've only had windburn once in the past when I had a fan blowing up through the canopy, but there's a couple of signs of it in the two corner plants.

SD
Click to expand...
Usually symptoms of wind burn beginning are leaf edge roll up almost like a taco. It’s where the humidity around the leaf surface differs greatly to the leaf itself and causes the roll up to preserve water retention at the leaf surface.

again this could be combated using VPD charts etc but is easily dealt with by relocating the offending fan if you can.
 
M

MintyDreadlocks

Well-Known Member
Renfro said:
I have definitely seen wind burn occur, that said the wind needs to be direct and rather intense.
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Have a 6" boost fan blowing directly on seedlings. never had wind burn. Maybe because i use wind block on my plants. :dunce:
(personal experience. sounds like bs to me.)
 
Renfro

Renfro

Well-Known Member
Wind burn is basically dehydration. High RH% will mitigate wind burn. Dry air will exaggerate it.
 
M

MintyDreadlocks

Well-Known Member
jondamon said:
Usually symptoms of wind burn beginning are leaf edge roll up almost like a taco. It’s where the humidity around the leaf surface differs greatly to the leaf itself and causes the roll up to preserve water retention at the leaf surface.

again this could be combated using VPD charts etc but is easily dealt with by relocating the offending fan if you can.
Click to expand...
So at that point is it a issue with your fan or humidity?
Renfro said:
Wind burn is basically dehydration. High RH% will mitigate wind burn. Dry air will exaggerate it.
Click to expand...
So its more or a less a issue with your environment and your humidity than it is the fan blowing directly on a plant. If you have good RH and mitigate the effects you're fine.
 
Renfro

Renfro

Well-Known Member
Anyone that says wind burn can't happen with cannabis simply hasn't enough experience to have seen it occur. You could have a fan blowing directly on a plant with 65% RH and not see anything negative but at 45% RH the same situation will cause windburn.
MintyDreadlocks said:
So its more or a less a issue with your environment and your humidity than it is the fan blowing directly on a plant.
Click to expand...
Is it a problem with the environment? I suppose that depends on how high you like your RH% during late flower. I for one keep it below 50% to avoid bud rot. To each their own, as long as you have happy plants all is well.
 
M

MintyDreadlocks

Well-Known Member
Renfro said:
Anyone that says wind burn can't happen with cannabis simply hasn't enough experience to have seen it occur. You could have a fan blowing directly on a plant with 65% RH and not see anything negative but at 45% RH the same situation will cause windburn.

Is it a problem with the environment? I suppose that depends on how high you like your RH% during late flower. I for one keep it below 50% to avoid bud rot. To each their own, as long as you have happy plants all is well.
Click to expand...
fair enough
 
jondamon

jondamon

Well-Known Member
MintyDreadlocks said:
So at that point is it a issue with your fan or humidity?


So its more or a less a issue with your environment and your humidity than it is the fan blowing directly on a plant. If you have good RH and mitigate the effects you're fine.
Click to expand...
Probably a little of both because my fan is at the opposing end of my room compared to my humidifier.

I only tend to see the issue about 5 or 6 weeks into flower where plants are big enough and leaves are plentiful that they hang right by the fan and my humidifier is off most of flowering time.
 
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