A question about 12/12 lighting

[kingfish]

Crow, if you grow Autos, non of this will be an issue.

[Crow]

Daylight hours in Maine, in September, will be 12 hours +/-15 minutes as the month progresses, based on sunrise and sunset times. STILL - there will be light for at least an hour more on either end to compromise full darkness, so at best, a 14 hour light to 10 hour darkness scenario (and really too cold to be growing outdoors).

I understand the negligible effect of moonlight but my question remains - How is growing under grow light so different as to make light leak such a critical factor? In a situation like mine in which there will be no artificial light leaking but if I don't cover the spacing in my floorboards and block the ends of my rafter tails above - just as outdoors, though even darker - I will have some ambient day light creeping in - certainly in the morning - before my grow lights come back on.

Not looking to be argumentative, I'm just looking to understand. I will not risk light leak - too easy to fix and so I will.

Chefbjy to your point about flipping to 12/12 being a plant stresser - would it be better to ease into the change from 18/12 over a one or two week period?

Thanks all for chiming in.

Crow

[Crow]

The outdoor grow took twice as long? Wow - I wouldn't have imagined. Did the quality suffer too?

[alltatup]

Fascinating!!

[Chefbjy]

The autumn equinox will be in September this is where the light of day if reduced to 12 hrs even 11 hours. Days get shorter and nights get longer. Some outdoor growers also use some form of light deprivation to initiate flower earlier because of weather conditions. The times adjust incrementally rather then just flipping a switch to 12/12 which is a form of stressing the plant.

I wouldn't risk light leaks imo. The moon has a different wave length of light not useable by plants much like a green light. DrPhoton could elaborate more on the subject.

[9fingerleafs]

I think it all comes down to time. Outdoor plants may not hermie because plants know the regular sun cycle and seasons. They know when winter is coming. But they take a lot more time to flower than plants that get the actual 12 hours. I’ve grown outdoors the same 10 week strain and it took 5 months to ripen under 13 hours of light a day in average. And it never got actual darkness

[Crow]

Have been reading about light leaks in grow rooms. This topic surprised me as I had not thought about it and so perhaps explains my pitiful 1st grow (among other newbie reasons).

Anyway - checked out my new grow shed that has lots of natural air flow and YUP - light infiltration. AIR FLOW = LIGHT INFILTRATION - so I have a bit of work to do before I switch over. Will need to figure how to block light BUT NOT BLOCK the air flow.

THE QUESTION OF THE POST however is: Where in nature can a plant get 12 hours of absolute darkness??? I'm not even considering moonlight BUT where in the US (let alone the rest of the world) can anyone find 9PM to 9AM of complete darkness (or any other 12 hour block)?

How is growing under grow light so different as to make light leak such a critical factor. In my situation I won't have any artificial light leak easily from 8:30PM to 4AM but after that, as the sun starts to rise, day light will sneak in incrementally for 3 or 4 hours before my 12 hour dark period is over. I'm convinced that I need to mitigate that but still I ask - why are plants grown outdoors not subject to that same darkness requirement?

Thanks for enlightening me. (Or is that - endarkening me? )

Crow