Strong weed smell at night

I found some old threads with a bunch of people laughing at the OP but I swear its true. About 2 minutes after the lights go out every night this heavy weed smell just starts pouring out of my closet. It permeates through the walls and actually stinks up the walkway outside my house.
Why do my girls smell so much stronger after the lights go out?
Fan runs 24/7. No changes in circulation when its lights out.
Growing OG Kush and Purple Trainwreck. 5 weeks and 5 days into flower.

I get that to

There's an occasional stink of herb outside my (terrace) house as well.
It's not me; I'm fully scrubbing.
It's not the neighbors, they've moved..and I know the others
Maybe filters do some weird not-working-shit with the temperature suddenly going down?

Plants do respire at night. It does not require light to take place. This is a process of releasing energy, kind of the opposite to photosynthesising. Photosynthesis is the preparation of the dinner, respiration is the dining process and the belching and flatulence that follows. When a plant respires, it releases carbon dioxide ( at a lower rate than it takes in ), oxygen, heat, water. It occurs on a cellular level with all living things..

Yes, plants respire - they even take in and use oxygen at night. Transpiration increases with light, heat, and so on - so it happens much more in the daylight.

If I understand the daily cycle of a flowering plant, it makes, uses, and stores energy through photosynthesis, and converts some of that energy to trichome production at night. That's also the theory with darkness before harvest - more than just 12 hours. I'm not sure if that is true. If that's true, an increased odor would make sense. And if you sense an increased odor, maybe that's true.

cheechako said:

If I understand the daily cycle of a flowering plant, it makes, uses, and stores energy through photosynthesis, and converts some of that energy to trichome production at night. That's also the theory with darkness before harvest - more than just 12 hours. I'm not sure if that is true. If that's true, an increased odor would make sense. And if you sense an increased odor, maybe that's true.

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We interrupt the life cycle by not pollenating the pistilate plant. This interruption causes increased trichrome production to keep the calyx viable for reproduction as long as possible. Trichrome production is probly a 24/7 process. The only correlation I can see with harvesting after a dark cycle would be for aromatics. I know of some plants (herbs) that are harvested in the morning because of increased aromatics.

You can take the plant out of the wild but you can't take the wild out of the plant.

Just a theory but animals that would typically graze upon a plant such as deer are active around dusk. So as a deterrent, some plants amp up chemicals that disuade creatures from snacking on it.
Some plants do this to attract certain critters (moths, bats, etc.) but weed is a wind pollinated plant so it doesn't want things chewing on it.

topfuel29 said:

We interrupt the life cycle by not pollenating the pistilate plant. This interruption causes increased trichrome production to keep the calyx viable for reproduction as long as possible. Trichrome production is probly a 24/7 process. The only correlation I can see with harvesting after a dark cycle would be for aromatics. I know of some plants (herbs) that are harvested in the morning because of increased aromatics.

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The OP says that the odor hits right after lights out. (The plants are deprived a dusk cycle, though.) Some herbs peak at dawn. Apparently, there is some crepuscular shift.

As far as I know, the darkness is what triggers flowering. We go with 12/12 for ease, but it is actually a bit less depending on strain. We stagnate the life cycle by not pollinating the plant, just like we prolong the vegetative growth phase with extended photo-periods.

I get that too, but when my lights go off my carbon filter goes off too for the night.

Thanks guys. Seems there are a couple people experiencing this. I guess I need a good carbon filter next winter.

Crack the window and put some Rosemary in their and it will get better. Rosemary will also stop those little bastard ass mites. I also use a really cheap air purifier that does pretty good.

plants stink way worse when the lights are out no doubt, i have no scientific information but during the day plants take in co2 and release oxegen, in the night they take in oxegen and release c02 so the smell factor could have something to to with the amount of oxegen in the air. the"pharamone" theory sound quite viable too

I had this as well and now keep my filter running 24-7. what i also found was that the smell was traveling through the intake in my room ( not the tent, normal room AC/heat intake). so when the heat in my house was running, at night, it was sucking the smell in and transferring it to the rooms with intake after it before hitting the heat pump. I sealed off the intake in the room my tent sits in and that took care of it.

topfuel29 said:

Plants do respire at night. It does not require light to take place. This is a process of releasing energy, kind of the opposite to photosynthesising. Photosynthesis is the preparation of the dinner, respiration is the dining process and the belching and flatulence that follows. When a plant respires, it releases carbon dioxide ( at a lower rate than it takes in ), oxygen, heat, water. It occurs on a cellular level with all living things..

Click to expand...

Funny, layman's terms.
Good explanation though.

Interesting. I have never experienced this but this is my first full indoor grow, past years always moved babies outdoors before any flowering. When the lights go off and if the temp drops a bit and the humidity rises the stoma would open. Not sure if that could be a factor. Maybe the air gets more humid without the drying effect of the lights. To me odors are more pronounced in humid air.

high humidity would lessen charcoal scrubbing ability a little i would think.

Is it a fresh green smell or actually bud smell?

If it's a fresh green smell, what you are smelling is Chlorophyll. From what I understand, when the sun goes down (lights out), the plant inhales CO2 but exhales Oxygen and Chlorophyll. Some say the level of Chlorophyll released depends on how much light has been absorbed during the day. If the plant is getting heavy/too much light during the day, it will exhale more Chlorophyll at night. I've been noticing this a lot recently when switching from 200w CFL to 400w HPS to 600w HPS. The smell was minimal on my 200w CFL but really strong after the 600w was turned on for late vegetation stages. Apparently, it doesn't exhale Chlorophyll all night long; just in the first few moments of lights out. I'm no expert, but this is where my research on 'lights out smell' has led me.

I am vegging some fairly low odor J Herer related strain and about 30% of the plants will up and produce that great smell of skunk and fruit....I kill that 30% because the wife's relatives will drop by short or no notice. There is no ryme or reason, the plants will up and belch that extra strong odor that my small- disguised as a Honeywell pollen remover- charcoal filter If I do get enough lead time I will give my girls a Neem Oil shower. Needless to say that is a last resort option.

my current grow is doing this big time....as soon as the lights go out the smell becomes very strong....it has actually woken me up within minutes of the lights going off.

but funny thing is the extra extreme smell will taper off to a normal smell within 30 minutes

Terps and Trichomes grow after lights out.