Too much CO2?

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Well-Known Member
Jun 26, 2011
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My friend is in week five of veg and she just got her CO2 installed, switched it on to 1000PPM, and then two days later all of her plants have down curled leaves, bottom, middle, and top. The new growth is also kind of coming in strange but I recognize this as the accelerated growth from using CO2 injection.

This down curled leaves thing is kind of disturbing, it looks like the plants are in high levels of stress. Did she need to ease her plants into into the CO2 at lower levels?

The plants are under 1000watt metal halides, about two feet away, in an air conditioned room, temp 76F and 46% humidity. She's using compost tea and Age Old grow right now.

Anyone heard of this?

Def a good post. I'm wondering what the appropriate CO2 starting point for plants in late stage veg (two months, extremely bushy each with 20 to 30 tops, 3.5 feet tall) would be. Has anyone else started plants off at 1000PPM and had this reaction? And most importantly, did they recover? I've lowered the PPM to 700 and applied B12...anything else I can do?
I edited my original post and included a pic.. very depressing
That looks like they are either over or under watered. All of them have drooping and undercurling leaves. It looks like IMO that the CO2 injection along with AC, 1kwatt lights, (and fans?) have all worked together to really dry them out bad. Are they different strains there? the middle looks like it may be more susseptable to the issue at hand.
Thanks, HP... I tryna figure out what her watering schedule is, but I'm pretty sure she waits until they dry out and then waters them... She's an experienced outdoor grower and everything is very steady in her room as far as temps and humdity (76/40). Indeed, some of the plants are showing more of the down curled leaf syndrome than others, with one or two showing none at all. She's growing Kush and Grand Daddy Purps. It _is_ a sealed room with AC tho and I was readying something one time about too much pressure buildup in a room potentially causing down curled leaves but I can't bring up the post......
I just read that you need to supply fresh air every four hours to a room that has CO2 in it.. is that true?

I always thought you just did a sealed room with ac and then turned the CO2 off at 'night' anyone know?

They're suggesting that curled down leaves could be caused by too much CO2 and not enough oxygen.
If she is at 1000ppm then its not too much.

Are the plants all yellow like they look in the picture?
@Growdude no.. that's the HPS lighting.. the system has one hps in it....
Not sure about refreshing air every 4 hours that is supplimented with CO2, that seems redundant to me but I'm not that well versed in CO2 supplimentation. I do know that The need for oxygen in the grow room is for the roots of the plants, so yes yu do need oxygen in the room but if the plants are transpiring properly during lights-on then they will produce plenty of O2. The only way yu could have a problem with that is if the room is extreemly tight and yer releasing a lot of CO2 from a compressed tank without exausting any pressurization of the room that would occur.

Also...In the pics, those leaves don't look so much curled under as just drooped like they are thirsty. I would suggest watering liberally (with proper PH'd water) one plant and give it a few hours to see if it changes from the rest

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