Permissible light leakage during flowering?

My googlefu is lacking today...

Are there any studies out there on flowering cannabis and light leaks?

Working on a project where I want a viewport - glass, fairly heavily tinted one side. The other side I was thinking PDLC (the new electric tint) film. But even that is more opaque than solid...

Wondering if theres any real data available that puts numbers to the problem so I can work through coatings/sizing etc with some confidence.

Thanks in advance!

How bright is the moon on a clear, full-moon night in the Fall where you live? And yet photo-period plants still thrive there, no?

Hey Hep - Ive read but never tested absolutely no more than .5 lux. Ive personally screwed myself with .8 lux. Wether thats strain dependant i do not know. A bright moonlit night is i think around .3 lux. Could you put a fabric hood on the port so you can exclude light but still take a look perhaps?

Flying Monkey said:

Hey Hep - Ive read but never tested absolutely no more than .5 lux. Ive personally screwed myself with .8 lux. Wether thats strain dependant i do not know. A bright moonlit night is i think around .3 lux. Could you put a fabric hood on the port so you can exclude light but still take a look perhaps?

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.27lux was what i read, but doesnt get into wavelength spectrum etc.

moose eater said:

How bright is the moon on a clear, full-moon night in the Fall where you live? And yet photo-period plants still thrive there, no?

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Yes but I dont want to grow the equivalent of outdoor plants... I dont want seedy weed. Preventing polination and development of hermaphrodites becomes pretty important in that case...

Thats the difference.

I peek in on my girls all the time when the lights are off. Just don't have a spot light lit behind you, or use a bright flashlight. I use dim light from (often) a shaded corner, and sometimes add an otherwise frustratingly dim flashlight to any queries during their night times..

If and when I get seeds, it's due to taxing the plants with nutrient imbalance.

This last crop, with 3 strains going, none went seedy, and the mix had too much N, as well as more than a few other excesses that taxed them, and still... no seeds.

Nope, I take that back; there was ONE California Indica plant, and I didn't prune any of the plants to the typical 8-10 inches below the canopy (the way I normally would), and with the density, etc., and the plant retaining its lower branches well below the tops (right down to the base), and only a single 315 cmh lighting the 4'x4' box, the tiny, premature, 'under-buds' that normally wouldn't exist, produced maybe 25 seeds on that -one- plant.. Which I attribute mostly to light deprivation and some 'nute unhappiness' on a more dense plant among that group of that specific strain, rather than any light leakage, as none of the others, including the remainder of the CI, had any seeds.

My crudely made 6-mil black poly exhaust hoods, stapled around several PC fans on each the boxes, provide the shading Flying Monkey was referring to, imo, and such plastic over a port on a dimly lit side of a box/cabinet, would likely suffice well.

Like I wrote above, I have a dimly lit flashlight that I would've tossed years ago, weer it not for this specific function, and I either use it, or, in the past, I would put green transparent film over the end of a slightly brighter light. No issues related to that operation.

A couple of issues to consider here:

1) Gradual switch to flowering times (i.e. 12/12)
Moonlight is not as much of an issue for flowering photoperiodic plants; one reason, is there is NOT a rapid cut of light hours to 12/12 from veg phase (18/6, 20/4, 24/0), but rather a more gradual switch (and typically a gradual increase of red spectrum)...so some weak moonlight is not a problem.

2) Light intensity; (in general) The light effects of the moon, at many thousands of miles away, is not as intense as a grow light, 3 feet away.

3) In my experience, a very small number of very minimal light leaks, interruptions (i.e. Some goof (or yourself) opening up grow room / exposing plants to light) is usually not much of a problem. However, lots of leaks or a minimal leak over a long period could be disasterous (unless you like hermies and or seeded buds).

My grow room builds were built with the principal of no leaks, so before plants went into flower chamber light issues were already eliminated. I never had any hermies or other issues.

Also, I never tell people,when I grow, so no random goof can open up a room to light. ( I have had friends, in their youth would show off their grow to all their buddies....causing problems, not least of which were rips, hermies, etc.)

Conclusion: I reckon that if you can keep the light leaks to a very small number, with a very small amount of light penetration over a very short time period then you could have minimal problems. Ideally, create room with no such problems.

I guess the original question might be analogous to the following question:
How many holes in the hull of my boat would still allow it to keep afloat?....It depends....where they are?....where do you plan to travel (open ocean?.....probably best to stay close to shore in case it takes on water really fast or to plug any and all holes before setting out....etc.)

Decision might be how much risk are you willing to take on to have sub-optimal environment?
If you are okay with the crop going hermie, then sub-optimal room, might be okay. On the up side, if the leak doesn't cause problems,,then you are golden.

Otherwise, get room sorted first (i.e. No light leaks) then grow.

I tend to be risk averse, so I first take precautions and I opt for the latter option. (Decades of grows, never had one go hermie.) Your mileage may vary.

Hee hee Ill try not to take offense at the infrence that outdoor weed is seedy and shite. Few people believe my outdoor isnt indoor these days. 23 outdoor seasons and multiple strains per year and ive only had 1 outdoor plant from solid known genetics hermie and it was caused im pretty sure by termites hollowing out the stem in early flower. From bagseed and plants withknown hermie traits thats a different story. .27 might be a lux level you can be confident of because a good chunk of the moon cycle is greater than this so maybe thats a good level to stick too.

Im with you moose eater- not just cause im envious of your quality diet and samon stocks. I also mix things up a bit- managing seed plants and germination and others and clones and what not all in the same tent. Im basicly outdoors with a tiny bit of tent support but early starts and preventing clone confusion etc has had me playing with this stuff a fair bit.

Del i agree with most you say but observe if we work with lux or foot candles [cause im a dinosaur] its a measure of known intensity so moon or candles or hps dont make much difference. Joys of a lux meter.

Hep couldnt you just look at them with a green light.

Depends on the strain of hermie you’re growing.
I had blueberry/WW that would always throw a few seeds on the lowest branch.
Good smoke. I’d plant the seeds and get another hermie.
Self substaining.

Do not know what it measures in lux. But the pilot light of the natural gas CO2 generator mounted on the wall of my room throws light. Enough so that the room is by no means pitch black. Have long been more inclined to think hermies are (more often than not) caused by stress and or genetics rather than light leaks. Only ever had one (regular seeds) plant throw a few balls and it was one of five White Widows but the only one to do so. Rather confident it was due to over fertilization (stress) and not the blue light dancing on the wall.

Leaks only effect TGA strains.....

Del_9_THC said:

Otherwise, get room sorted first (i.e. No light leaks) then grow.

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Well technically cabinet I'm working in the era of legalization is half being designed around showing it off.

Like i said in the first post I want a big window in the door. Just trying to resolve whether the PDLC (aka smart tint - apply power to make it clear) and a stardard tint, will block enough to eliminate issues.

But i can't seem to put my hands on data that actually put some numbers and wavelengths to make it a math problem.

Flying Monkey said:

Hee hee Ill try not to take offense at the infrence that outdoor weed is seedy and shite.

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None intended - just saying different environment. Comparing to outdoors doesnt always apply...

Pretty much all the weed I grew up on was outdoor vancouver island goodness which beats the hell out of the "big pharma" crap that i can legally buy.

The strains we have today bear little resemblance to wild types. So comparing to nature doesnt get us far - these are man made hybrids with crosses that could never occur in nature.

But none of that really relates to the whole point which was do we have any hard technical data on where the risks start.

The old Growtron from the 1980-1990's had see through sides, did plants hermie in that?

Hermies = Shitty genetics poorly selected by greedy, unprofessional Scam artists that calls themself "Breeders".

The world of Cannabis seeds saw in the last decade an insane proliferation of fake breeders that sells random F1s that come from casual pollinations of hybrids of hybrids of hybrids...

Results = dozens of phenotypes in one "strain" some good, some bad, some hermy, meanwhile you are paying top dollars for em....

Im not an expert in genetics and I have a hella lot more to learn but I definitely think that the main thing to avoid hermies is getting seeds from someone that really did the job in selecting em...environmental stress is very relative .

On you tube there a video of a guy showing how one of his flower room at night receive light from another flip flower room....with a good strain...no hermies!

My room no light leeks, I keep the fan on low without stressing on the canopy too much and yet some Bubbas Gifts from Humboldt seeds put out so much nanners that it looked like a straight male!!

Dinafem also gave me so many hermies with the Dinachem and the RemoChemo....

As far as permissible light leak numbers I don't have idea...but the common idea seems to don't shine nothing too bright on the plants...a little reflecting on the wall seems fine.....but I would def take care of any of it

https://www.youtube.com/watch?v=QO8AHI7-k6o

Frosty Nuggets said:

The old Growtron from the 1980-1990's had see through sides, did plants hermie in that?

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I've seen a few current and past setups where its been done with/without tints and a few current ones that are currently using similar pdlc glass. But no real word on whether it causes issues or not...

@grapefruitroot - yeah... I'm hoping under the more legalized era we can start to see some better genetic development. I've got a good friend who wants to start working with cannabis DNA (his day job involves breeding GMO genetics for plant based insulin) - but is stuck in the paperwork hell dealing with the canadian government... Looking forward to seeing what happens when the professionals can start working on the genetic sequences.

Hermies = Shitty genetics poorly selected by greedy, unprofessional Scam artists that calls themself "Breeders".
P

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Well, I do agree that there a lot of greedy unprofessional breeders and scam artists (not sure if I would rather deal with a "professional" scam artist or an "unprofessional" scam artist?�&#56832, this is nothing new in the cannabis world.

Actually, many South East Asian landrace varieties, like various Thai ones, could, indeed, exhibit hermie traits....so, not necessarily due to scam breeders, but your point is taken.

The real money in cannabis is in the seed selling. Why do you think the cannabis cup (Talk about scam artists....High Times..haha) always went to only a few select firms?.....Then golly gee, they sell seeds at $15.00 (or more per seed) ....yikes!.....Think how many seeds one pollinated female plant could produce.......then with the "femenized" seeds, ...Female plants stressed, chemically or otherwise, to go hermie, and then using that "pollen" to cross with other female plants.....possibly reinforcing hermie traits (especially if it did not take much stress to get the feminization process) in the offspring....yup that sounds like a scam.

Hephaestus,

My main point was, how much risk the grower is willing to take on in an experiment.

If the grower wants to go with proven techniques (I.e. No risk), then they may not experiment.

OTOH, If you have other grows ( hopefully we'll far away from any that might cause pollenation) then it might be interesting try it.

Flying monkey,

Thanks, I know about lumens, Lux, foot candles, and so on (optics in highschool physics 11 was a large part of the syllabus, ....and then more learning about light in uni physics).
I would still submit that a close grow light would exert much more influence than a far away reflected light from the moon. (All else being equal, Intensity is proportional to inverse of distance squared...)

I would not rubbish outdoor grass; my first 20+ years of growing were all outdoor, due to there being no commercially available lighting systems in those days. (and then when some were available, horrendously over-priced for my budget.)
Indeed, if done well, outdoor grass can be spectacular....

But, unlike indoor grown where the grower has complete control of the environment, outdoor growers have to put in much more effort to produce outstanding buds than an indoor grower.
(North of the a certain lattitude (or south, if in Southern Hemisphere), some form of light deprivation, is typically required to get plants to finish when the weather is still reasonably dry and not humid.....that is a lot more work than simply switching on/off the lights for 12/12. Hence, if they do not know what they are doing AND are not willing to put in the extra effort, some outdoor growers will produce mediocre buds.

Flying Monkey said:

Hep couldnt you just look at them with a green light.

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Seems simple enough. Perhaps with some white light added, to the tune of 0.27lux.

If it's really just for posing, have two tents, and just show the one with the lights on.

Having no idea what's actually happening, does tie my hands somewhat

Del_9_THC said:

Flying monkey,

Thanks, I know about lumens, Lux, foot candles, and so on (optics in highschool physics 11 was a large part of the syllabus, ....and then more learning about light in uni physics).
I would still submit that a close grow light would exert much more influence than a far away reflected light from the moon. (All else being equal, Intensity is proportional to inverse of distance squared...)

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All good brother - happy to wonk out on the physics with you just dont want to derail thread.

Now i know this is for a weed display kinda system its got me thinking Hep. So im clear you want a vendor display kinda arrangement to show of your plants. You only want to see them during their daylight cycle. If this is correct could you use a mirror film filter on the glass specified to cut out the full light amount of light from the viewing room-standard room lighting is low intensity compared to the grow room, so transperancy wouldnt be an issue during the plants night cycle. When the lights were on you would see the plants in detail as they would be in higher intensity light with some light losses.