Does CO2 increase flowers significantly?

LST: 3 plants
1st pic Gold leaf
2nd: super silver haze
3rd: Purple Haze
Grown in a no till soil with live red worms
Seriously? By adding CO2 will it significantly increase yield? I current have over 60 dense sites


Short answer? Yes! Long answer? You need to do a lot of things to make it worth the effort.


Nice job!!!

Beautiful I got 2 of each going in veg right now…Nice job!

Here’s what I know for sure co2 adds up to 25% more yeild . But that’s saying that you know that with hps
400w = 8oz.
600w= 16 oz
1000w = 24 oz
And a light mover adds another 25% more , hope this helps. Good luck

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The most important thing to know about CO2 is that it only helps if you have a LOT of light. Your plant will photosynthesize faster with more light, up to a certain point. Then increasing the light does no good because available CO2 limits the reaction. If you add more CO2, then it can increase the rate.

So first of all you need so much light that the plants can’t grow any faster. Then if you want to add CO2, it can help. But you need to have a closed system, or all your CO2 is quickly lost. No more ventilation fans dumping heat outside. You probably need to have a dedicated air conditioner and humidity control. All of this complexity is why CO2 is usually only added in big commercial greenhouses.

For a hobby personal-use grower it makes little sense. It makes your grows a bit faster and yields a bit more, but aren’t you already growing more than enough for yourself and your friends?


Bigfella, Just my wife and I: occasionally barter. Two grows a year. Been purchasing seeds from different company. Wish this company offered pick and mix.

They do have some preselected mixes. I guess they thought those different strains were good to compare. I don’t have any idea how they select them.

@WhYNot I have used Co2 in my last 2 grows out of 4with all off the right conditions and :warning: it is definitely worth it here is a photo of some for an indoor grow and just my opinion but it will also help you if your temps for any reason go a little higher.

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It’s 25% extra at the time for harvest :slightly_smiling_face:

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And does your grow tent have an exhaust fan that goes outside? If it does and it changes all the air in the tent every 10 minutes then I think the volume of CO2 you are generating does nothing to raise the concentration of CO2 inside the tent. It all goes right out the exhaust and is replaced by room air with the normal CO2 level.

I suppose if you have a closed air system with the generated CO2 staying in the one room, you could raise the level a bit. You could calculate how much if you know how much you generate and the room volume. Then you need an airlock door so you don’t let it out going in and out.

I’ve actually generated very high CO2 levels in my grow chamber with dry ice for fumigation purposes and the exhaust fan clears it in minutes when I unseal the chamber and turn the fan on.

I have a complex system. Been designing and redesigning for years. Now it’s simple with unique plumbing and separate controllers for fans and exhaust fans. All depends on flow of water if I want my grow area warm cool or cold depends on time of year.
By listening what you are saying and the quantity I grow, I don’t really need the co2. My next grow will be 4-6 main colas on each plant and not so LST. I’m always trying to outdo myself each grow.

Please people Co2 is and to be used with great :warning:️ caution definitely if you are going be use in your home or any inside set up. The boots buddy bag has a very strong small so as soon as you walk in use think Co2 be careful the exhaust fan will take it out of a room but I am lucky that I do not have to have my on only maybe for a bit when I water and the it go’s back on its timer.

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Yeah, the ultimate CO2 generater is a car engine running in a sealed garage! Generating lots of CO2 can kill you, but plants don’t need anything like that concentration. When I have used dry ice to generate lots you could feel it when you opened up the grow chamber, but still not pass out. Running a little gas burner to generate it may be very dangerous unless you have a monitor that measures and keeps it to a safe level.

For sure though, if you are going to cobble up some home brew generator, make sure your grow room is absolutely sealed off from your home.

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Really you would bring it that far an all off the tragedies and suicide out there take it a little bit more seriously just be careful that’s all I’m saying.

Or maybe you have already put your foot in it by saying something like if it has happened to that person already very insensitive and nothing got to do with growing what is all this shit.

I have to agree with @1BigFella on this.

The best numbers I’ve seen thrown out from any scientific type of study were UP TO 20% yield increase. If I remember,that was at a ppfd of 1200 umols with co2 concentration of 1500 ppm. For reference, that’s the biggest baddest 1000 watt hps bulb in a 39”x39” tent with 4-5 times the ambient co2 levels. At least that’s where they measured the 20% increase in yield.

The point at which you can start to see a measurable increase in yield is around a ppfd of 500 umols. To see that increase you have to actually maintain a co2 of about twice ambient, before you need more light to use the excess co2. And the gains there won’t 25% or even 20%. Backing up, the key word there is maintain. In order to do that, you have to introduce that much co2 and then hold it at canopy level. If you’re running exhaust, it ain’t happening.

Obviously everyone is free to spend their time and money however they please. But if you want to get the highest yields out of your grow, there’s probably a better way for most. The point of diminishing returns on light for most rooms is going to be around a ppfd of 800 umols. That means that you can still grow more weed with more light, but on a grams per watt basis your yield will start going down. That’s based on ambient co2 levels. So you can spend money on light alone up to that point. If you’re there or above, pump all the co2 you want. But remember that if you’re exhaust is running, all you’re doing is evacuating the co2 you’re generating.

There’s lots of info available on this if you search the web. But if you find the big time commercial grows supplementing co2, you’ll almost always find that they’re sealed climate controlled rooms.

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@dbrn32 the only help that I am trying to give is in a certain part of the world temperature and humidity is now almost just right, now mine you not just this year there has been a change over the pass 4 to 5 year’s I’m not complaining, the Co2 I’m only trying to to give some advice on the likes off the boots buddy sealed bags or even just the pads and for sure the boots buddy has worked for me that my 2 cent about it.

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No problem.

How certain are you that it was the co2 that showed the improvements, and not just a higher yielding pheno, healthier plant, different feeding, or one of countless variables that could’ve contributed to your increase in your yield?

Beyond that, the real point of my post was that it’s entirely possible for your lighting to be in a position where your grow can benefit from additional co2. While 10 others may not. It’s definitely not something you can apply a blanket statement that adding co2 will help your yield. It can under the right conditions, absolutely. I just wanted to bring those conditions to light before 100 different members went out and spend their money on something they may not understand.


@dbrn32 at this stage you know light water and Co2 are the major factors in extra yield and the reason for my opinion in the increase of your yield is because when I introduced the CO2 to my grow I could see with my own eyes the difference is that ok

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