A question about 12/12 lighting

[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

[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

[alltatup]

Fascinating!!

[Crow]

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

[9fingerleafs]

Yes the quality was lower but I think it was because of the high temp and humidity of outside. It produced almost double than the same size pot indoors. That strain was not high quality “highly hybridized” from a breeder. It was from outdoor grown “regular” weed endemic to the region

[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.

[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

[Chefbjy]

There's not really any side effects to just flipping the switch in my experience. However if you reduce the amount of time gradually it will have a little more stored energy before it starts flowering. I'll look into how the grow light differs from sun but someone may already know that answer.

[kingfish]

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

[Crow]

Thanks - that's an option for sure BUT I still want to understand the why of it

[DW2]

Howdy Crow, I have learned that the ambient light from street lamps, porch lights, the momentary light that gets in when entering or leaving the grow room, and maybe even from passing car head lights made a difference in my grows. I have installed 'black out' curtains over the windows and placed one at the entry to the grow room to allow entry into the room without the 'flash' of light from the door opening and closing. These measures has seemed to help the plants. Now when inside the room, I can not see my hand in front of my face where as before (after a few moments) I could see some details in the room.

[Crow]

Helping the plants thrive is certainly what it's all about.

[Toripony]

I don't know the answer but I sort of touched on this topic from a different direction before... I wanted to know what triggers cannabis plants at the equator to flower since the day length doesn't vary. The answer I found was that they do it when they get good and ready, kind of like an Auto, except that a plant might veg for up to 2 years before deciding to flower. The article (which I can't locate right now and cannot speak for its accuracy) went on to say that this is only true in a very narrow band and that even a couple hundred miles north and south of that band there's enough variance in the day length for the plant to have a "rhythm". It also stated that plants grown at different latitudes have developed different genetics. This makes me wonder if the plant is always trying to revert to it's "natural" (not really) state despite it's adaptation to varying day lengths, so any light it gets during a night while flowering makes it try to revert. Perhaps there's a constant state of tension and depending on brightness, duration and a particular plant's sensitivity it gets pushed past the tipping point. Just theorizing; I'd really like to know, too. I'm sure somebody somewhere knows, but I haven't found it yet.

[Crow]

Thanks - pretty damn interesting!

The inquiry continues...

[PuravidaC]

I too have wondered about "complete" darkness and have read that even indication lights on equipment in grow room can throw plants off. I have taken great pains to make my grow room light proof only because that is what I have read. Not sure about your set up but I painted the inside of intake ducts flat black to help eliminate light infiltration!

[Crow]

This is an outside - through the door view of my little "cannabis cabin", aka, grow shed.

You can see the open rafter tails and gaps in the floor boards. Both the floor and the rafter tails are screened over with 1/2" hardware cloth to keep
out critters - mostly red squirrels and also keep them from setting up house under the building.

I definitely will need to shade the open areas without cutting off air circulation. I have fans on but they would be of little use just pushing inside
air around.

Photo was taken a couple of weeks ago. Since then the 5 plants (Northern Lights) have had their 1st manifold, the lights (600 watt LEDs)
have been lowered and the still young Northern Lights are branching out beautifully.

They will be moved into # 7 or # 10 (haven't decided yet) Smart Pots well before turning on for flowering. That, AFTER I darken
the room.




Crow

[Crow]

You are pretty much seeing the entire inside . The room is less than 8' long x 4' deep. The door is 30" wide so that gives you an idea of the scale.
I think I will only have room in there for 4 plants once I size up to bigger Smart Pots set on the floor.

The bare wood on the back wall is part of a hinged panel that covers a 24" wide window. Ran out of the foil to cover the entire panel as the panel was an after thought, so as you can see, I duct taped what foil I had to the ply panel.

The window has been propped open very day for the past 2 weeks. Has been really hot and humid. Even with open window, 2 fans, and other planned
ventilation, the day time temps have been hovering in the low to mid - 80°s F.

It's kind of an indoor/outdoor grow room hybrid.

[yellow]

Interesting... have you considered sheeting the walls and painting them white?

[Crow]

No - I like the industrial space age look + it was less work. I have wayyyyyy too many projects. Had to keep this one manageable.
Seems to be working better than fine.

[kingfish]

Damn Crow, that is on hell of a Man Cave.

[Crow]

Thanks KF. It's just a shed I built under the porch - repurposed, from lawn furniture keeper to Crow's Nest.

Cheers - Crow