I see all lot of set ups where there are no fans blowing directly on the plants and it has made me curious. Should I have fans blowing directly on my plants? I could understand that if you have enough air being moved in the room and ambient airflow moving through the plants then it would be fine, but I’ve never seen any actual explanation as to why it’s being done. What do you have to say Over Grow?
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Lots of fresh air is a good thing. I keep the air moving just above the plants. Don’t think it helps to hit them too hard The young ones toughen up with moving air too 
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The fans blowing on them also make the plants sway slightly strengthen the stems to be able to support the bigger buds they develope. 
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If your fans don’t move (oscillate) then they shouldn’t point directly at plants, they will get wind burn. If fans are fixed it’s best to have them blowing indirectly off a side wall etc.
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One of my clip on fans I’ve pointed upwards towards the tent roof and turned it on full. It’s enough to hit the roof and distribute it enough to make the tops of the plants move. Good call on the wind burn. It can make a mess of your buds. A friend had to trim a good quarter from the tops of his colas at harvest time as it had took the moisture out of them. I never asked him how well it smoked
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lol wish i had in my pocket what i spent on fans over the years. I have a hate - hate relationship with the things.
Nowadays i use 140mm (5") computer case fans angled so they blow off the side walls. I make a wire frame for them to keep them off the walls because they will blow themselves flat against the side if not. They can easily be speed controlled and are very quiet and last way longer than monkey fans etc.
Indirect air movement always gets me the best results but at the top of a space/tent you have warm spent air and it’s not good to blast that about too much or you could end up recirculating some it through the plants 
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My filter and extraction is over kill for the flowering area. At the minute though I’ve had to move the tents to a different room so I’m no longer drawing air from outside. I’ll have to keep a closer eye on them. I’m getting a little bit to relaxed since I bought my auto pot system and basically only check the plants if I remember to. The humidity, temp and voltage are all checked via phone.
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It’s too cold and wet here most of the year to only use outside air so i use house air but have a window partly open most of the time so it gets mixed with some fresh. My intake duct just sits on the floor till the weather finally gets warm, then it gets pinned up just below the open window with an old sock over the end to keep those crappy critters out 
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Yeah mine is drawing and filtering into same room and it’s made my area a little warmer but not where it’s a problem. They are just feeding more.
Normally with drawing from outside it’s around high 70s. Meh it is what it is. They are growing (maybe a little to well) so let them continue without messing on
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I have a 3 speed reverseable ceiling fan in the room over the plants. Seems to help with circulation, I can reverse it if needed if I think the plants are getting too much wind in one direction or the other. I have not had any ‘known’ issues.
Regards,
mike28086
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Fan’s are IMO only for air movement, to prevent stalle air in the grow enviroment.
Fresh air for the plants, support better growth in your plants but prevents growth of mold/meldew
Evens out the tempreture, and can cool the canopy.
Also lowers the humidity a bit, mixing up the hot n cold air layers.
Abosolutely no reason to blow air on the plants, to get them to move and build stalk.
Unless your making rope, it makes more sence to me to support them with a trelis
And have them focus their energy, on making pretty flowers and less stick.
So a breach of air strong enough to remove “dead zones”, is enough for the plants to be happy in the enviroment.
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I learned decades ago that the leaf uses up the CO2 around itself in around 5 minutes or so and so you need to replace that air with fresh air that has more CO2 in it, which means at least some regular airflow over the leaf surface.
As said above though, too much will dry out your leaf and burn it. We also can put in support netting or other support so the energy used to make big stalks for support can go to making buds.
As also said, if the air is too still and humid, that leads to mould.
Somewhere in-between is the sweet spot but how to decide where that is?
At the same time as I was learning about airflow, I was learning about how close you should place your HPS lights and the same advice was given for both and other factors, but no numbers were said.
Pretend it is a lovely summer day, the breeze is lovely, the sun is lovely, it’s not too hot, it’s not too cold, It’s not too windy, it’s not too still, it’s not too dry, it’s not too humid. It’s lovely. If you close your eyes (and ignore the noise of the fans etc), you could imagine yourself in a summer meadow surrounded by nature. The sun warms your skin, the breeze keeps you cool, both in combination are just about right. You don’t get too dry after a while, you also don’t start getting damp.
That is the environment you should engineer in your room to grow cannabis. Cannabis will do very well in a room you also would enjoy being in.
Just close your eyes and feel if everything is right.
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@Esrgood4u my man for flowering your vpd is right on a good place, in my opinion flowering is from 1.1 to 1.6 and you are at 1.3 your kind of ina the middle sweet spot, they will be drinking a lot water
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Yeah I’m filling the 47 litre barrel every 2 - 3 days for the 6 girls in the autopots @GreenCaciqueHawaii. The ones in normal pots with coco I’m hand watering every other day.
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@Esrgood4u Yes as soon you get the vpd in between ranges ,plants get ridiculously and start to grow super fast, as soon i correctly leaved my grow area between ranges, pm dissapeard plants started to grow faster and respond much better ane had to start water daily even if plants were in soil they were drinking really fast
I got tired of fighting temps and now is easier to control l, 8f get hot just spray some water to raise humidity and days that is really humid i keep em mostly dry, we forget thet get water from the atmosphere too
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@Esrgood4u. Simplento use practical and let me know were my plants are really standing
I’m a big fan of having a large amount of air exchange via vortex fans threw vented hoods and then a supplemental oscillating fan mounted to a wall to provide some occasional stronger gusts to move around the room.
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