How much light during dark is too much: flowering

[LEDman]

Greetings!

Searching for the terms "light+flowering" (and related) gives tons of unrelated threads, so I apologize if this question has been posted before.

During the flowering cycle, you want your plants to be in total darkness once the lights are off. But, cannabis being a weed that naturally grows under a sky illuminated by stars and the moon during night, must have a certain tolerance to low light at night - hell, I've read about outdoor crops going into flowering after a couple of really dark, stormy days.

I know that using a low-wattage "green" bulb is a good way to illuminate your flowering chamber without putting undue stress upon your plants.

Is there any scientific data how much light (lumen or PAR) may safely reach the leaf surface and not trigger a re-veg?

 

[Maer]

The hormone that causes flowering is destroyed by light. The way I understand it the plant produces it throughout the life cycle and when it builds up to a certain concentration the plant flowers. I don't think light leaks or low light will cause it to reveg, but it may slow down your flowering (although one member ((LUDA)) said that's not true)

 

[G-Dog]

This is an interesting topic. I have asked about the moon many times in another board and it went unanswered. Many times people "think" they have a lighting leak because their plant turned hermi, but I theorize that is a natural reaction to sensemilla or just a genetic disposition. You have guys like DJ Short spending a lot of time trying to get a hermi disposed strain of Thai to stop, but it later surfaces in the hybrids that he created from them. Rez Dog as well. It is so easy for a breeder to just blame an amateur grower when it could be the expensive genetics he is using.

 

[LEDman]

Yeah, I'm not that worried about hermies, it's just my fear of disrupting the flowering cycle that makes me wonder how much light is still viable.

But then, I realise that nothing about plants is digital ("on/off"), but rather analog, gradual in nature. I guess that's a good thing to keep in mind - most of the time, it's not "yes/no", but rather "a bit less of this/a bit more of that"...

 

[G-Dog]

The OP stated a digital type of question. Some plants don't depend on photo period what-so-ever. Most genetics these days are a hybrid of the extremes. Hard to put your finger on what is right and wrong these days with all certainty. The rule books all say to not let light get into your dark cycle and very little light will interrupt the flower cycle. Best to do the best you can with that and hope for the best. I have not ever been very careful and I do not have the problems people have on these boards.

 

[LEDman]

Indeed. My flower room, as it turns out, is not 100% light-proof; once my eyes have adapted, I can still make out dark shapes. Still, it's much darker than on a clear night outside - I guess that genetics will determine whether or not that poses a problem or not.

My White Widow started flowering in the veg room about a month ago, while none of the others did. Now, two days in flowering, most of the rest of my plants have tiny pistils coming out of their nodes, so I guess they got the message. Keeping my fingers crossed...

 

[ConqueringLOJ]

Hey LED,

That is a great question. I have always heard that during lights-off period they should receive no more light than they would on a full moon night if they were outside. But I have never seed that equated to a lumen or PAR rating. I just try to keep it as dark as possible in my room so as not to disrupt the cycle.
It would be interesting to take a light meter outside on a full moon night and see what the data says.

 

[Maer]

0.27 lux Full moon on a clear night

Source: Wikipedia

 

[ConqueringLOJ]

0.27 lux Full moon on a clear night

Source: Wikipedia

Cheers!

 

[LEDman]

Yeah, I guess that must be the maximum permissible light level for cannabis grown outdoors. With indoor strains that have been hybridised and grown indoors for... literally hundreds of generations, I don't know if that is really true anymore.

I'm gradually putting more and more black tape around the edges of my frame to make the dark... more dark.

 

[G-Dog]

Yeah, I guess that must be the maximum permissible light level for cannabis grown outdoors. With indoor strains that have been hybridised and grown indoors for... literally hundreds of generations, I don't know if that is really true anymore.

I'm gradually putting more and more black tape around the edges of my frame to make the dark... more dark.

With the investment of time and money that we put into this it is always best to err towards safety.