TOO MUCH LIGHT!

Jellyfish · Nov 11, 2017

I switched from CFL's to LED lights not too long ago. My first run with LED's went fine, but on the next two, I kept lowering and lowering the lights, to get them as close to the tops as possible.

By the time I got to the third run, my fan leaves were yellowing and falling off. By the end of that run, there were no fan leaves left.

I just would not believe that the problem could be too much light, because my temps were fine, yes, even at the top of the canopy.

I had to end that run a little early because without fan leaves, there was no more growth.

AFTER that run, I did some research and discovered that, YES, it IS POSSIBLE to give your plants TOO MUCH LIGHT. Even when the temps are down.

So this run, I have the light 18 inches over the canopy like the manufacturer suggests. And things are going much better.

I'm posting this in case somebody might have a similar problem.

This article explains everything- PSA: Too Much Light?*****
*****Okay, as Ronin4life pointed out in post #2, the link doesn't work. But you CAN use your favorite search engine to find it, searching under "PSA: Too Much Light?" The article is on a website called grow weed easy dot com. Thanks to Ronin4life

Ronin4life · Nov 11, 2017

Thanks for info...the link consent work for me.

growingcrazy · Nov 13, 2017

I am just going to toss this out...

This summer I did some testing with vegetable seedlings that were started indoors under hps...

I wanted to see the results of putting 2 groups of plants outside, one hardened off as usual, the other directly into sunlight. I divided the full sun group into 2 groups also, one that was left alone as control and one that got magnesium foliar sprays.

End result was that the plants that got the foliar had very little issue with going to direct sun, the other half struggled and started to show def. before they came back around.

Not conclusive but it satisfied my hunch.

Long story short...You can feed to match the light intake if all other parameters (temp/humidity/moisture) are met. Within reason of course...

EDIT: I am not sure who did the PSA test, but you can see that the plants have similar def. each time... This isn't the plant or the light in this instance, just the grower. Increasing EC doesn't mean the plant is up-taking what it is in need of.

repuk · Nov 13, 2017

It can, definitely. Just had to replace a previous HML I built for a previous grow on a different space; when used on a veg tent (garden shed grow in my sig) my plants cooked... so I'm replacing it with fluorescents.

Veg tent height is 60cm/23", running a string of 10 XM-L's (at 90W total) cooked the plants leaves, I raised it and even at full height it's clear the plants are not digging it. It will be a different story if LED chips were 3W (XM-L's are 10W), so individual LED power has to be taken into account also, not overall power only.

I'll be using 110W for the fluorescents and from previous grows I'm positive I can lower them until they almost touch the canopy and all leaves be perky and happy.

Jellyfish · Nov 13, 2017

I agree- with fluorescents, you don't have to worry about too much light or heat.

StevenJennings · Nov 16, 2017

Yeah man. I was noticing tht some of my canopys nugs were smaller than the othere but were closer to the light. Bumped em up a few inchs and they started to fill and maintain growth. Dont let em go too long or you can bleach your nugs and ive heard tht it takes taste and potency away from nug. Not from experience. Just read it somewhere. Prob on here. Lol. I let my canopy have 18-24 inch from my cobs and they flourish. Too much light is a thing. I never experiemced this until using led as well.

Jellyfish · Nov 16, 2017

StevenJennings said:
I never experiemced this until using led as well.

Right, because they don't give off much heat, they fool you. For my TWO ViparSpectra 450's, 18 inches is the MINIMUM I can have the lights close to the plant tops. Thanks for your comment, StevenJennings!

f-e · Feb 5, 2021

Old thread but..
Using essentially 450w of LM301 LEDs was going fine sat over a meter at about 6 inches. I lifted them a few inch and went to 550w to get the tops back to ~65000lux on my particular meter. The tops, while no more illuminated, snapped shut. Leaves moved from horizontal solar panels, to pointing at the lights to reduce catchment. The serrations rolled a little to further slow water transport through the plant. Some in the canopy also moved to pointing upwards.

I had bumped it up as a critical kush had reached the light at 100,000lux and shown no issue. It still showed no issue. While the kush fv was trying hard to avoid the light.

This happened in about 4 hours. An hour later, some had decided to risk it a bit and open a little. Barely though.

I have seen this over and over. At about 65Klux / 550w really low, the leaves in buds will point upwards, roll a little, darken as they take on too much feed, and break out in a rash. The buds themselves will 'flat-top' refusing to go closer to the light. These are just a couple of tops generally and must suffer for the greater good.

Perhaps this offers a little more insight for people pushing with there LED's

flylowgethigh · Feb 6, 2021

A way to measure leaf temps is on my shopping list. I saw the same reaching upward with too much light on baby sprouts, and raised the lights. 250 umols at the leaf seems about right for sprouts.

Horselover Fat · Feb 6, 2021

f-e said:
Old thread but..
Using essentially 450w of LM301 LEDs was going fine sat over a meter at about 6 inches. I lifted them a few inch and went to 550w to get the tops back to ~65000lux on my particular meter. The tops, while no more illuminated, snapped shut. Leaves moved from horizontal solar panels, to pointing at the lights to reduce catchment. The serrations rolled a little to further slow water transport through the plant. Some in the canopy also moved to pointing upwards.

I had bumped it up as a critical kush had reached the light at 100,000lux and shown no issue. It still showed no issue. While the kush fv was trying hard to avoid the light.

This happened in about 4 hours. An hour later, some had decided to risk it a bit and open a little. Barely though.

I have seen this over and over. At about 65Klux / 550w really low, the leaves in buds will point upwards, roll a little, darken as they take on too much feed, and break out in a rash. The buds themselves will 'flat-top' refusing to go closer to the light. These are just a couple of tops generally and must suffer for the greater good.

Perhaps this offers a little more insight for people pushing with there LED's

I can let my tops grow to about 6" from the leds and they are fine. Any closer and they are not. Perhaps if I dropped EC a few points they might be able to take a bit more, but for now it seems 6" is as close as I can take them. My phone measures about 65000-70000 lux at 6". Pretty similar results to yours.

GoatCheese · Feb 6, 2021

Yea, the high intensity photons from modern white leds/cobs seem to need a fair bit of clearance between them and the plants in order for the molecules in the air to dissipate some of the energy from the photons before they with the surface of the leaves.
..using abit of calmag also helps to keep the leaves to stay in better shape.

I have Cree CXB3590 cob lights and it took awhile till I figured how to use them. In my tent/veg cab I can’t turn the lights much hotter than 25-30 watts per cob if I have 60 cm clearance to the plants or the leaves will start suffering.

Horselover Fat · Feb 6, 2021

GoatCheese said:
Yea, the high intensity photons from modern white leds/cobs seem to need a fair bit of clearance between them and the plants in order for the molecules in the air to dissipate some of the energy from the photons before they with the surface of the leaves.

That doesn't happen. Wall losses do happen as the light is reflected off the walls.

GoatCheese · Feb 6, 2021

Horselover Fat said:
That doesn't happen. Wall losses do happen as the light is reflected off the walls.

English isn’t my first language so I hope I explain this right.
Energy of rays/radiation is being dissipated by atmospheric gasses. It happens to the photons coming from the sun but also to the photonic energy from leds/cobs.
..use your head before you start talking back.

Also, in reality light/photons aren’t reflected off the surface, in reality other photons are emitted off the surface as higher energy photos hit atomic matter.

Koondense · Feb 6, 2021

You got it pretty wrong GoatCheese...
Dissipation is another thing than dispersion in space, reflection is not emission.

Cheers

Horselover Fat · Feb 6, 2021

GoatCheese said:
English isn’t my first language so I hope I explain this right.
Energy of rays/radiation is being dissipated by atmospheric gasses. It happens to the photons coming from the sun but also to the photonic energy from leds/cobs.
..use your head before you start talking back.

English ain't my first language either, but what you describe doesn't happen in your grow space. Only reason you lose intensity as you go further from your lights is wall losses due to the light spreading out. Yes, going through atmosphere will absorb some photons, but your light is so close to the plants that it doesn't have an effect.

CannaRed · Feb 6, 2021

I would think it's not the air. That only happens in nature when the sun has to travel through miles of atmosphere.
Inside we have to deal with the Inverse Square Law

GoatCheese · Feb 6, 2021

Koondense said:
reflection is not emission.
Cheers

IF you put a red object close to a white wall and aim white light in their direction, why do you think you see some red on the white wall when the light was also white.

Horselover Fat said:
Yes, going through atmosphere will absorb some photons, but your light is so close to the plants that it doesn't have an effect.

Either air (atmospheric gasses) affects photons or it doesn't .Which one is it, cause you’re pretty much claiming both things to be true at the same time.
I didn’t claim photons from the COB lose ALL THEIR ENERGY, but some – enough for the leaves not to suffer.

CannaRed said:
That only happens in nature when the sun has to travel through miles of atmosphere.

You can breathe inside your grow area, right. Plants use CO2 indoors too. Nature is also inside your grow area as are atmospheric gasses.
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In nature particles are way more sensitive to change than your minds seem to think they are. Look at the shadows and colors inside your living rooms this evening and try to think about how sensitive photons are to change. ..hit a bong few times if you have to.

Horselover Fat · Feb 6, 2021

GoatCheese said:
IF you put a red object close to a white wall and aim white light in their direction, why do you think you see some red on the white wall when the light was also white.

Because the red object absorbs other wavelengths and red gets reflected.

Either air (atmospheric gasses) affects photons or it doesn't .Which one is it, cause you’re pretty much claiming both things to be true at the same time.
I didn’t claim photons from the COB lose ALL THEIR ENERGY, but some – enough for the leaves not to suffer.

You do understand there is a difference between few tens of cm and kilometers? Get a piece of glass and it's rather translucent. Now stack 20 pieces and it's going to be much less translucent. The distance between your light and your plants is so short there is no effect.

In nature particles are way more sensitive to change than your minds seem to think they are. Look at the shadows and colors inside your living rooms this evening and try to think about how sensitive photons are to change. ..hit a bong few times if you have to.

Shadows can be different color, but it's because they are lit by different colour light source. Very visible here on a sunny winter day as sun lit snow is white and shadows on snow are extremely blue.

GoatCheese · Feb 6, 2021

Horselover Fat said:
Because the red object absorbs other wavelengths and red gets reflected.

But if the white light is intense enough you will see a white light also coming off the red object, not just more intense red color.
Same effect is on the waxy leaves on your plants; in mild light they appear just green but when the white light source gets intense enough you will start seeing that white light coming of the leaf too, a “white light hot spot”

This is cause the surface gets saturated enough from the white light photos to start being re-emited off that surface when new white light photons, with slightly higher energy, hit them. Is repelling the right word? like same polarity magnets/ or charges will repel each other

Horselover Fat said:
Shadows can be different color, but it's because they are lit by different colour light source. Very visible here on a sunny winter day as sun lit snow is white and shadows on snow are extremely blue.

The blue comes from the color of oxygen which is blue. Oxygen gives oceans their blue color

Horselover Fat said:
The distance between your light and your plants is so short there is no effect.

You keep contradicting yourself. If 1000 meters of atmospheric gasses have an effect on photonic energy then so does 10 cm; if 10cm of those gasses have NO EFFECT on photons, as you just claimed, then why would 1000 meters affect them.

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This is getting maybe too much off topic, and i start to lose interest in repeating the same thing over and over again.
= Even 1 cm of atmosperic gasses has a miniscule effect on photons, wether your mind understands it or not.. end. off. Peace.

Horselover Fat · Feb 6, 2021

TOO MUCH LIGHT!

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