Too much light? Upward-curving leaves and foxtailing

Hi all,

I’ve grown three cycles without any issues in a 40x40 cm grow with a 120W quantum board using Samsung L301H LEDs.

I decided to upgrade to an 80x80 cm grow and added a second 120W quantum board. After that, I ran into problems. In the last cycle, I had upward-curving leaves, foxtailing and lots of seeds.

In this new cycle, when I switched to flowering, the same issues started again.

There are no pests; I did a thorough inspection with a 60x magnifying glass. The temperature inside the grow is between 24°C and 27°C at the plant base with the AC off, and I have a fan blowing at the top and an exhaust fan. I’m watering with pH 6.2 to 6.3, doing organic growing, and there’s no over-fertilization.

I fixed all the issues from the previous cycle, but the problems persist.

The only variable that stayed the same is the amount of light. I started with 20% power on each quantum board, and just before switching the photoperiod, each was at 50% power. So, 4 days ago I removed one quantum board and set the remaining one to 60%, since I read that too much light can cause these problems, even if it’s not too hot.

I don’t have a ppfd meter, only the cell that’s not accurate.

If that’s not the issue, I don’t know what to think anymore.

Do you guys think it’s possible that they’re like this because of too much light only?

If it's only happening towards the top of the canopy and your heat is in check I'd definitely say it's a light issue.

Petinha88 said:

Hi all,

I’ve grown three cycles without any issues in a 40x40 cm grow with a 120W quantum board using Samsung L301H LEDs.

I decided to upgrade to an 80x80 cm grow and added a second 120W quantum board. After that, I ran into problems. In the last cycle, I had, and lots of seeds.

In this new cycle, when I switched to flowering, the same issues started again.

There are no pests; I did a thorough inspection with a 60x magnifying glass. The temperature inside the grow is between 24°C and 27°C at the plant base with the AC off, and I have a fan blowing at the top and an exhaust fan. I’m watering with pH 6.2 to 6.3, doing organic growing, and there’s no over-fertilization.

I fixed all the issues from the previous cycle, but the problems persist.

The only variable that stayed the same is the amount of light. I started with 20% power on each quantum board, and just before switching the photoperiod, each was at 50% power. So, 4 days ago I removed one quantum board and set the remaining one to 60%, since I read that too much light can cause these problems, even if it’s not too hot.

I don’t have a ppfd meter, only the cell that’s not accurate.

If that’s not the issue, I don’t know what to think anymore.

Do you guys think it’s possible that they’re like this because of too much light only?


View attachment 5431124View attachment 5431125View attachment 5431126View attachment 5431127View attachment 5431129View attachment 5431131View attachment 5431132

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Check very closely under your leaves to check for mites. Use a loupe.

I use 150w for that footprint. I learned it would be 222w if to match my 3x3 light viparspec thats 900ppfd pretty much every inch of tent at 12”. This would be 240w usually when I cram a light meant for bigger space in a smaller one, I get foxtails once. And tacos.

I never seen them like this though holy cow. Hope it gets figured out but Id for sure take one of those lights out stay at 120w 100% at what ever distance its meant to be. Usually raising them starts to even out their ppfd foot print.

More light is better they say of course but Im probably going to be raising/dimming my viparspec. Have to dial it in, plants cant just accept all that light. My veg plants suuuuper dim lighting. My flower plants do fine just giving enough light.

I am experimenting giving more like with my viparspec but Im aware it doesnt work like youd think at first being new. Heck Ive grown for a while Im still considered new.

I know for me photone is accurate. It has 2 ways to measure. Using your camera and ALS(ambient light sensing). I know if I set it to camera instead of ALS, and put a piece of white printer paper over the front camera as a diffuser, it's within 8 PPFD of what my manual says it should read. Have you tried that method? I was truly impressed.

.Smoke said:

If it's only happening towards the top of the canopy and your heat is in check I'd definitely say it's a light issue.

Click to expand...

The new leaves that have grown in the middle also curved upwards. The old ones did not.

curious2garden said:

Check very closely under your leaves to check for mites. Use a loupe.

Click to expand...

I did that and its clean. I bought a loupe thinking its mites

medidedicated said:

I use 150w for that footprint. I learned it would be 222w if to match my 3x3 light viparspec thats 900ppfd pretty much every inch of tent at 12”. This would be 240w usually when I cram a light meant for bigger space in a smaller one, I get foxtails once. And tacos.

I never seen them like this though holy cow. Hope it gets figured out but Id for sure take one of those lights out stay at 120w 100% at what ever distance its meant to be. Usually raising them starts to even out their ppfd foot print.

Click to expand...

medidedicated said:

I use 150w for that footprint. I learned it would be 222w if to match my 3x3 light viparspec thats 900ppfd pretty much every inch of tent at 12”. This would be 240w usually when I cram a light meant for bigger space in a smaller one, I get foxtails once. And tacos.

I never seen them like this though holy cow. Hope it gets figured out but Id for sure take one of those lights out stay at 120w 100% at what ever distance its meant to be. Usually raising them starts to even out their ppfd foot print.

Click to expand...

Now i have to wait about 1 or 2 weeks to see. I removed one light, the remaining one is in 60% and 12 inchs from the top of the plant.

These pics i took to compare next week to see if they are recovering or getting worse

bignugs68 said:

I know for me photone is accurate. It has 2 ways to measure. Using your camera and ALS(ambient light sensing). I know if I set it to camera instead of ALS, and put a piece of white printer paper over the front camera as a diffuser, it's within 8 PPFD of what my manual says it should read. Have you tried that method? I was truly impressed.

Click to expand...

I admit that I never thought about "calibrating" the photone. When I get back home I will do this. Thanks

Legit there was no calibrating friend. I just put "Light Sensor"(bottom setting) to camera instead of ALS. Then I have a little piece of white paper I press and sort of stretch with a thumb on either side, to minimize any gap between the screen/camera and paper. My phone is pixel 6a, so hopefully you have a device that the feature functions with.

bignugs68 said:

Legit there was no calibrating friend. I just put "Light Sensor"(bottom setting) to camera instead of ALS. Then I have a little piece of white paper I press and sort of stretch with a thumb on either side, to minimize any gap between the screen/camera and paper. My phone is pixel 6a, so hopefully you have a device that the feature functions with.

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I understood. When i said “calibrating” i meant using the correct config (led full spectrum) and a diffuser.
I thought that even using it wrong, the ppfd values wouldn't be very different if I used photone in a generic way.

I will measure it correctly and inform the right values here
thanks again

Petinha88 said:

I admit that I never thought about "calibrating" the photone. When I get back home I will do this. Thanks

Click to expand...

It's worth it, I have an Apogee and a Photobio and with the diffuser on my Photone app my app was always 100 PPFD off. It was a stable amount off at both high and low points. So it worked for me.

PS it read high and I was only using 20# bond when they recommend 24# bond. I'm sure that would have dialed in the error better. Nota bene, I'm on an iPhone hth.

curious2garden said:

It's worth it, I have an Apogee and a Photobio and with the diffuser on my Photone app my app was always 100 PPFD off. It was a stable amount off at both high and low points. So it worked for me.

PS it read high and I was only using 20# bond when they recommend 24# bond. I'm sure that would have dialed in the error better. Nota bene, I'm on an iPhone hth.

Click to expand...

Right, like my last grow I tried photone without doing any settings, and then just referenced the initial reading to gauge how much I increase PPFD.

Wish I'd done it this proper way the first time. I do imagine your phone's camera sensor plays a role in how accurate it is. Let us know mate! Look up the PPFD chart from your light manufacturer to know how off or accurate your phone is with diffuser

bignugs68 said:

Look up the PPFD chart from your light manufacturer to know how off or accurate your phone is with diffuser

Click to expand...

Great idea

curious2garden said:

It's worth it, I have an Apogee and a Photobio and with the diffuser on my Photone app my app was always 100 PPFD off. It was a stable amount off at both high and low points. So it worked for me.

PS it read high and I was only using 20# bond when they recommend 24# bond. I'm sure that would have dialed in the error better. Nota bene, I'm on an iPhone hth.

Click to expand...

bignugs68 said:

Right, like my last grow I tried photone without doing any settings, and then just referenced the initial reading to gauge how much I increase PPFD.

Wish I'd don't it this proper way the first time. I do imagine your phone's camera sensor plays a role in how accurate it is. Let us know mate! Look up the PPFD chart from your light manufacturer to know how off or accurate your phone is with diffuser

Click to expand...

I use an iphone 14.
I will do this test, cause now i see how important this is.
Will do it tomorrow (away from home today) with and without the diffuser and the correct and wrong type of light selected on photone.
My light chart



I was using 2 of this light, now only 1. The second one i started another plant in the old 40x40cm grow.

I dont do organic soil I do drain to waste coco so I wouldnt be suprised if its soil related but yea just a thought. I read the whole post twice and was as stumped as you until I noticed the double light comment.

While its not horrible its just a little overpowered for the space Id just get a viparspec thats meant for 2.5x2.5 like a mars hydro ts1000. Having a lot of height would be nice Im flipping my 3x3 plant now and oof 6’ tall isnt quite enough even with fan/filter on top.

Just thought about how I did 130w in a 2x2 and it got real hot and some crisp growth no fox tail but pushin it.

medidedicated said:

I dont do organic soil I do drain to waste coco so I wouldnt be suprised if its soil related but yea just a thought. I read the whole post twice and was as stumped as you until I noticed the double light comment.

While its not horrible its just a little overpowered for the space Id just get a viparspec thats meant for 2.5x2.5 like a mars hydro ts1000. Having a lot of height would be nice Im flipping my 3x3 plant now and oof 6’ tall isnt quite enough even with fan/filter on top.

Just thought about how I did 130w in a 2x2 and it got real hot and some crisp growth no fox tail but pushin it.

Click to expand...

I suspected the soil was the issue, so I replaced it entirely for this new cycle, but the problem persists.

I'm quite confident that it's a lighting issue.

One question I couldn't find the answer to elsewhere: If the problem is resolved, do the tacoed leaves return to normal?

Hmm. Id say it might let up but if its crisp it might be toast. People say yellow leafs cant go green again but I do it routenely with clones. A near death leaf outgrowing the damage. Can turn back green to some degree. But tacoes it depends how bad it got.

I dont get tacos really so hard to say based on what Ive seen myself.

One thing that makes me think it may not be the light is I think you said youve been dimming them but the lower leafs taco too which unusual. Also that your temps are perfectly fine.

Petinha88 said:

Hi all,

I’ve grown three cycles without any issues in a 40x40 cm grow with a 120W quantum board using Samsung L301H LEDs.

I decided to upgrade to an 80x80 cm grow and added a second 120W quantum board. After that, I ran into problems. In the last cycle, I had upward-curving leaves, foxtailing and lots of seeds.

In this new cycle, when I switched to flowering, the same issues started again.

There are no pests; I did a thorough inspection with a 60x magnifying glass. The temperature inside the grow is between 24°C and 27°C at the plant base with the AC off, and I have a fan blowing at the top and an exhaust fan. I’m watering with pH 6.2 to 6.3, doing organic growing, and there’s no over-fertilization.

I fixed all the issues from the previous cycle, but the problems persist.

The only variable that stayed the same is the amount of light. I started with 20% power on each quantum board, and just before switching the photoperiod, each was at 50% power. So, 4 days ago I removed one quantum board and set the remaining one to 60%, since I read that too much light can cause these problems, even if it’s not too hot.

I don’t have a ppfd meter, only the cell that’s not accurate.

If that’s not the issue, I don’t know what to think anymore.

Do you guys think it’s possible that they’re like this because of too much light only?


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Click to expand...

Yes. These photos show a classic reaction to too much light.

That shape is referred to as "canoeing" or "tacoing" and the plant is doing that to reduce the surface area that's being impacted by light.

Having multiple boards will help give an even light cast so I wouldn't say that you should remove a board but you should reduce the wattage and/or increase the hang height.

A lux meter (Uni-T at Amazon) is well worth the $20±.

[edit]

I replied as soon as I saw the first posting. I've scanned the thread and it looks like you're using Photone. Ouch. When I tested Photone (Korona back then) the programmer didn't even specify what weight paper to use. Since then, I've tested Photone and found it to be 16% high.

Between that and the absolutely atrocious DLI values that they recommend, I don't recommend Photone unless you can calibrate it against a known good source.

Another strike against Photone is the need for the diffuser. There's no getting around that because it's needed to overcome the fact that a light meter in a phone is designed for a very different purpose than the sensor in a light meter. For a phone, only the directly incoming light is measured vs a light meter which uses a parabolic cover to gather light coming in from all angles. The idea of putting a paper strip on is referred to as a "kludge" in the software world (I've been writing software for a living for 30+ years including 3 for Apple so I have some understanding of what Photone is doing behind the scenes).

Photone sells a diffuser which adds almost the price of a light meter to the cost of using Photone but, if a grower wants to use Photone, I would think it's money well spent.