End of flower, temp vs ppfd vs co2

Hey everyone, was hoping to get your thoughts on this.
I have my 4x4 with 750w of SF LED, so I also have CO2 to help the plants absorb all that light.


But, of course with CO2, it needs to hotter for the plant to efficiently transpire and breathe. This means i run about 80-85°
Once I get to the last few weeks of flower, I want to fade my bud for some good bag appeal and bring out those purples in my GDP. One of the ways I will do this is by lowering temperatures.
At what point does my CO2 have diminishing returns as the temp goes down?
As the use of CO2 efficiency goes down, will my plants begin to struggle photosynthesize the amount of light i am giving them to the point they will burn and stress?
Do you normally turn down the lights during your grow the last week or two?

I run HLG QBs which are very similar to yours, and I always dim my lights over the last week or two of flower for the very reasons you state. I grow a lot of strains that tend to purple and I like to help it along with low temps and low rH if possible (with the added benefit of boosting trichome production a bit) at the end of flower. By the time I'm on my last week I typically have my lights dimmed to about 75% of max and tend to see plant stress if I don't.

NanoGadget said:

I run HLG QBs which are very similar to yours, and I always dim my lights over the last week or two of flower for the very reasons you state. I grow a lot of strains that tend to purple and I like to help it along with low temps and low rH if possible (with the added benefit of boosting trichome production a bit) at the end of flower. By the time I'm on my last week I typically have my lights dimmed to about 75% of max and tend to see plant stress if I don't.

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Do you feel like you reduce yield at all doing this?
Obviously since this is what you do, you feel like the potentially smaller yield is worth bringing out colors?

I've never tried to measure the difference in final yield, but I think I am aided by the fact that i nearly always run the plants a week to 10 days past when a lot of people would harvest. By the time I drop my temps and light intensity the calyx have finished swelling and the flower is pretty much fully mature. I'd say I lose less than someone who was looking to harvest with less amber would due to delaying the light and temp drops. I just prefer the effects i get from my indicas when I push them out to 10 weeks or so.

NanoGadget said:

I've never tried to measure the difference in final yield, but I think I am aided by the fact that i nearly always run the plants a week to 10 days past when a lot of people would harvest. By the time I drop my temps and light intensity the calyx have finished swelling and the flower is pretty much fully mature. I'd say I lose less than someone who was looking to harvest with less amber would due to delaying the light and temp drops. I just prefer the effects i get from my indicas when I push them out to 10 weeks or so.

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I honestly think all 8 wk strains should go 10 and all 10 should go 12... lol

but im following this bc I like the comprehensive info on Co2 and light, learning. not running co2 just yet

NanoGadget said:

I've never tried to measure the difference in final yield, but I think I am aided by the fact that i nearly always run the plants a week to 10 days past when a lot of people would harvest. By the time I drop my temps and light intensity the calyx have finished swelling and the flower is pretty much fully mature. I'd say I lose less than someone who was looking to harvest with less amber would due to delaying the light and temp drops. I just prefer the effects i get from my indicas when I push them out to 10 weeks or so.

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What week of flower do you bring your light up to 100%?

ÒÒlegilizeitÒÒ said:

What week of flower do you bring your light up to 100%?

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I usually have my lights at 100% by the end of veg. End of veg I'm usually at around 18 to 20 inches from the the canopy at 100% and as flowering starts and progresses I lower the light gradually closer. By week 3 or 4 of flower i will have the lights about 12 inches from the canopy. Gives me a ppfd of around 950 in the middle and 825 ish over most of the canopy

maranibbana said:

I honestly think all 8 wk strains should go 10 and all 10 should go 12... lol

but im following this bc I like the comprehensive info on Co2 and light, learning. not running co2 just yet

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Agreed. Im of the opinion that cash croppers have created a mentality of fastest possible turn over.. everybody seems in a big hurry to harvest immature buds with underdeveloped calyx and white pistils all over the damn place..