Photo period and light leak

[dba1954]

I'm planning my first Photoperiod grow and ran across this article. It seems to say light leak isn't that critical? Can someone help me understand this as I have no practical knowledge of growing photoperiods.

Growing cannabis: Debunking the light leak myth

For those of us who are prepared to replace cannabis mythology with plant science, there are opportunities to improve yields by better understanding our plants’...

stratcann.com

 

[Emilya Green]

I don't much believe in the light leak theory either. They say that it can cause them to hermi, but I believe that in most cases plants hermi for other reasons. I have seen many examples of a veg station and a bloom station both operating in the same basement (different sides of course) without a tent or any kind of barrier between them.

Most of our lights direct their main beams downward, into the canopy. Light that is reflected into the area has several things going against it. First, it is reflected, at least once... and maybe it has bounced a few times. Each time the ray of light bounces, it loses a whole lot of energy, depending on the reflectivity of the surface it bounced off of. More important though, is the inverse square law, that looks at the distance between a light source and what it is affecting. Lets say your lights are 18 inches away from the canopy and produce a certain amount of light, X. Each time you double that distance, to get over to the other side of the basement, you lose 4x the original energy. If you have a garden at 21 feet away from the light source, you have doubled the distance that the plants are seeing the light from by 14 times, relative to the garden directly under the lights. If you are hitting the canopy with 40k LUX of light, the garden seeing that ambient light from 21 feet away can be seeing no more than .04 LUX, and less if it is reflected light. Moonlight is measured to be about .05 - .1 LUX. Plants grow just fine in moonlight, without hermying. I suspect that they can also handle a small light leak.

They say that lights on humidifiers and such in a tent can cause hermies. I have never seen someone prove that. I think more often it is bad genetics or stressing the plants in other ways that cause hermaphroditism. Light leaks are just a good excuse to use so that there is something to blame other than ourselves when things go wrong.

 

[bluter]

i'm mindful of light leaks but really don't worry about them. it has far more to do with weak genetics than the light leaks.

 

[SmokingWings]

I don't much believe in the light leak theory either. They say that it can cause them to hermi, but I believe that in most cases plants hermi for other reasons.

Your entire msg is spot on.

Light leaks are just a good excuse to use so that there is something to blame other than ourselves when things go wrong.

I had thought of that as a reason but I really believe that blaming the light leaks is a way for many of the early growers to explain something that they do not understand. Something along the way that early civilizations blamed the lightning and thunder on a particular god who threw lightning around in the sky.

Early growers did not understand why some female plants started to flower and produce seeds so blaming the lights was easy to do. The next person heard the reason and figured it sounded as good as anything else. It keeps getting repeated so often that many believe it to be true so why bother to actually check it out.

For the last two years I have grown in a tent with the top of the door flap left open a touch for air circulation at night. The vegetating area is 5 feet away and those lights are on for an additional 7 hours. No problems with plants suddenly turning into hermaphrodites except for one new plant.

That one plant started showing male flowers after the 3rd week of flowering which supports the genetic reason. None of the other 20 some other plants that went through the tent over the past two years did this. Yes, a few developed a couple of male flowers at 10-11 weeks after flowering started but that is more of a last minute attempt to reproduce. And, the solution to that was not to cover the light leak; I solved that minor issue by harvesting a week or two earlier. Guess what? No one complained that there was a problem with smoking that weed.

The one plant that produced the male flowers will be harvested by the beginning of next week. There are three clones from that plant but I am not sure what experiment to put them through but that decision is still several weeks away.

 

[bluter]

you don't even need to be all that light tight if you go room in room.

 

[Chrondocious]

Fwiw....ive kept 2 tents with the normal pinholes, and a cab I built, in the same 6x8 room that my moms were vegging in. The moms were blocked by some blackout curtains, and the "door" for the cab was a blackout curtain. The veg light more than seeped out of the top of the curtains. I could work in there with the curtains closed......never had a problem. Be careful, but those tent pinholes arent problems. Small lights from power strups and stuff inside the tent will fuck you up though.

 

[bluter]

Small lights from power strups and stuff inside the tent will fuck you up though.

i always put a little electrical tape over them. super easy fix. don't use a power strip with a lit switch though if you can avoid it. get one with an indicator light instead and cover it.

 

[Emilya Green]

I don't much believe in the light leak theory either. They say that it can cause them to hermi, but I believe that in most cases plants hermi for other reasons. I have seen many examples of a veg station and a bloom station both operating in the same basement (different sides of course) without a tent or any kind of barrier between them.

Most of our lights direct their main beams downward, into the canopy. Light that is reflected into the area has several things going against it. First, it is reflected, at least once... and maybe it has bounced a few times. Each time the ray of light bounces, it loses a whole lot of energy, depending on the reflectivity of the surface it bounced off of. More important though, is the inverse square law, that looks at the distance between a light source and what it is affecting. Lets say your lights are 18 inches away from the canopy and produce a certain amount of light, X. Each time you double that distance, to get over to the other side of the basement, you lose 4x the original energy. If you have a garden at 21 feet away from the light source, you have doubled the distance that the plants are seeing the light from by 14 times, relative to the garden directly under the lights. If you are hitting the canopy with 40k LUX of light, the garden seeing that ambient light from 21 feet away can be seeing no more than .04 LUX, and less if it is reflected light. Moonlight is measured to be about .05 - .1 LUX. Plants grow just fine in moonlight, without hermying. I suspect that they can also handle a small light leak.

They say that lights on humidifiers and such in a tent can cause hermies. I have never seen someone prove that. I think more often it is bad genetics or stressing the plants in other ways that cause hermaphroditism. Light leaks are just a good excuse to use so that there is something to blame other than ourselves when things go wrong.

Someone asked to see my math. I used an approximation of the exact formula, I=X/4^d!14
At 14 doublings of the distance, the divisor ends up being a little over 1 trillion on the last iteration.