LED light burn

sailorsport

New Member
59 days into my first grow. 1 Northern Light auto. 300w LED. My LED has a Veg and a flower switch. Veg light-93 watts, Bloom light-180 watts. About 10 days ago, I Initiated the Bloom light in addition to the Veg light. I am on an 18/6 indoor soil grow. From the 2nd day of Bloom light addition, I've had what appears to be classic light burn. I have now (progressively raising) raised the LED so that it is now about 30" from the apical bud. I have run out of room to raise it higher and the burn symptoms don't seem to be getting better. HELP!
 
Just a quick thought : anyone think it might help the situation if I just use the Flowering light for only 8 hr, and the veg switch on for 16 ?? Thanks !
 
That sound like something else and not lightburn.
I have 6 x 300W / 185W LED and I never got lightburn or a light bleach at the bud tip over 15" most under 10"

A pic would help very much.
 
Thanks for responding ! I am 67yo and not very up on tech matters. I have a Trac phone and really don't know how to post a pic. Many of the lobes of the leaves are yellow with the middle vein part and the tips are turned up and burned. I doesn't appear to be getting any better. I am 66 days into my 1st grow. The buds seem to be getting nice and fat. The leaves look exactly like the light burn pics on the "------------" site.
 
Really tough to tell without a picture. What brand of light? This far into the grow, 30" is pretty far. I get a P600 LED about a foot with little bleaching and that's late bloom. Help us and we can help you, a picture says a thousand words. I assume you're in soil?
 
Thanks for the help. I'll look into the possible cal-mag deficiency. Planning to go through your problem solver link later tonight . Never knew about LED-possible cal-mag deficiency.
 
Management edited my original post with the Brandname of my LED. Apparently that company caused a lot of problems on the site. 5 gal airpot mix of peat moss 60%, 25% perlite and 15 % ewc . I've been using 1/2 soiltab every 2 wks during veg and 1/2 flowertab every 2 wks during flower. Man at the hydroponic store suggested only running the flower switch ...... info on the LED site says the VEG switch can be used alone, but not the Flower switch..... the Flower switch should only be used in conjunction with the Veg switch. I appreciate any insight you might have. Thanks !
 
I tend to agree with Darkgrow, this sounds like a chemical burn from excessive N2 levels rather from light (UV). Excess Urea or Ammonium compounds do exactly what is being described here. LEDs aren't prone to causing this. (never unless they're shortwave UV for sterilizing)

A pic should be included.

I am actually taking a plant health course refresher right now, and excessive N2 damage is something we've been talking about this week. It's fresh in my brain.
 
Thanks for your interest in helping! The whole situation is crazy. Once again, I went to numerous pictures of excess N2, and that diagnosis doesn't seem to fit my problem. Sorry my responses are incomplete due to my not being able to include pics. The whole situation is an enigma to me. My LED source is 30" from the apical bud, and the fan leaves are pretty much yellow with the inner veins green. The tips of several of these yellow leaves are burn and curl upwards ..... I went back and read re N2 toxicity and the leaves are described as dark green. I'm going to harvest at first opportunity.... going to check trichomes and cut asap .... think that's a good plan?
 
I'm skeptical about the EWC % in your mix, and reading further into this there are numerous examples of ewc doing exactly what you're seeing. You really sound like you have got a classic text book case of burn (also referred to as scorch). Nitrogen toxicity symptoms usually start at the tips and leaf extremities and causes them (leaves) to curl and turn brown/tan. The direction of the leaf bend is immaterial.

See the bottom illustration in example in pic.

nutrient+deficiency+problems+in+plants.jpg


ewc is full of Ammonium and Urea compounds. It's extremely "hot" stuff. You should never exceed 10% conc. in your mix. Long established plants might be able to handle such a high N2 value, but a smaller plant, depending on the strain will show burn rather quickly as the imbalance in pH will attack the delicate roots. Actually I'd have gone 3.5-5% and no more. In this case, less = more ( safer)
 
Don't know about your feeding but 1/2 tab every 2 weeks sound strange.

How old is your girl and what say the breeder about flowertime ?

Don't know what light you have but sounds like the one I have (P300)
Anyway LED that have a bloom and veg switch use both in bloom.
In veg you can save some energy and the more blue spectrum helps with tight node spacing.
 
Thanks for the response. I'm going to read more on the possible ewc overload. Even if certain suggestions might not apply, I'm learning a ton of stuff that will help me eventually. I'm thinking of starting flushing for the final 2wks.
 
Thanks for being interested. P300 is correct. Northern Light auto plant journals suggest 75-90 days seed to harvest. The well-known seed site that I bought them from suggests 1 full tab per month, 1/2 in deep, around 7 in from the stem. Advice on an autoflower only site, several xpert growers suggested to use 1/2 tab every 2 weeks, to error on the side of caution. As per an earlier suggestion I watered with a light dose of cal-mag 3ml/gal. Today makes the 67th day from seed. Any suggestions/insight are greatly appreciated.
 
I feed 1t cal/mag to each gallon at each watering. I have not had any problems with cal/mag since I started this. :peace:

Which is why it's not certainly not Ca/Mg related and more than likely N2 overage.
Gradually upping your N2 levels is very important with any plant. You want very neutral conditions to establish strong roots, then after 4/6 ( strain dependent) weeks start introducing a bit more nutrition. This guarantees that you won't induce root shock/ nutrient burn or N2 scorch. I always recommend a slow release when doing a soil/ semi-soil medium. In hydroponics you'd use a slow incremental release of supplemental nitrogen, or what ever your soilless food you are using. Most of these products being N2 in the form of Urea /or Ammonium diHydrogen Phosphate based.
 
I'm skeptical about the EWC % in your mix, and reading further into this there are numerous examples of ewc doing exactly what you're seeing. You really sound like you have got a classic text book case of burn (also referred to as scorch). Nitrogen toxicity symptoms usually start at the tips and leaf extremities and causes them (leaves) to curl and turn brown/tan. The direction of the leaf bend is immaterial.

See the bottom illustration in example in pic.


ewc is full of Ammonium and Urea compounds. It's extremely "hot" stuff. You should never exceed 10% conc. in your mix. Long established plants might be able to handle such a high N2 value, but a smaller plant, depending on the strain will show burn rather quickly as the imbalance in pH will attack the delicate roots. Actually I'd have gone 3.5-5% and no more. In this case, less = more ( safer)


Disagree with what you say about EWC - I use it 25% in my mix and I run NO-TIL on my 10th round and I top dress with EWC at flip and even do several EWC ACT teas thru out my run. It's not hot... the chem tabs probably are tho.

Back to the OP issue - Its not going to be light burn or cal-mag (whatever that is) issues.

Could be as simple and senescence (fall leaves start to yellow and fall off). Some cannabis cultivars (strains) yellow after going from veg to flower. I run a strain that starts shortly after flip to 12/12. Let the leaves fall off.

Look at leaves like this:

Leaves have a 2 part life cycle. First part they are energy sinks - in that they absorb and store energy.

2nd part of their lives they are energy sources for the plant to feed the flowers so that the plant can reproduce.

The plant moves the energy from the leaves to the buds by translocation - meaning the plant has the ability to translocate minerals/energy ect. via its vascular system. As long as you are not stressing the plant she will put ALL her energy into building large pretty flowers. What we want right?

Cal/mag issues with LED - show me the science.

The chemical makeup of photosynthesis only has 1 molecule of Mg,I find it hard to believe there would be any issue there - specially since the OP is using EWC - plenty of cal/mag there. Easy enough... mix in a tbs of calcium (not cal/mag) in the next water routine. Sources of calcium = calcite, calcium, oyster shell flour, gypsum (food grade). I avoid egg shells, they require some extra work despite what you will read. This will not harm the plant unlike cal/mag which will start killing the soil microbes. Not what we want.

^^^ that all said, hard to trouble shoot without a pic but it sounds like the ladies are growing fine and you have a few yellow leaves. I worry about insects (spots on leaves), and insects... did I mention I worry about insects?? In a soil grow you should have everything you need. I'd stop with the tabs whatever they are...You should be able to get to the end with the soil you have going.

Flushing?? Whats that?

Read about Cation exchange here you don't have enough water to flush nutrients away without killing the plant first = fact. A hydro grow maybe but not a soil grow.

Cation exchange link - this debunks flushing soils:

Minerals are held onto in soil via cations and anions - positive and negative charges - water does nothing to either a positively or negatively charged mineral. This article also points at the negatives of having too much Mg in the soil. Since plants don't use or require much at all, adding in some extra Mg in most cases makes things worse for the soil and the plant.

Cation Exchange Capacity in Soils, Simplified
 
Disagree with what you say about EWC - I use it 25% in my mix and I run NO-TIL on my 10th round and I top dress with EWC at flip and even do several EWC ACT teas thru out my run. It's not hot... the chem tabs probably are tho.

Back to the OP issue - Its not going to be light burn or cal-mag (whatever that is) issues.

Could be as simple and senescence (fall leaves start to yellow and fall off). Some cannabis cultivars (strains) yellow after going from veg to flower. I run a strain that starts shortly after flip to 12/12. Let the leaves fall off.

Look at leaves like this:

Leaves have a 2 part life cycle. First part they are energy sinks - in that they absorb and store energy.

2nd part of their lives they are energy sources for the plant to feed the flowers so that the plant can reproduce.

The plant moves the energy from the leaves to the buds by translocation - meaning the plant has the ability to translocate minerals/energy ect. via its vascular system. As long as you are not stressing the plant she will put ALL her energy into building large pretty flowers. What we want right?

Cal/mag issues with LED - show me the science.

The chemical makeup of photosynthesis only has 1 molecule of Mg,I find it hard to believe there would be any issue there - specially since the OP is using EWC - plenty of cal/mag there. Easy enough... mix in a tbs of calcium (not cal/mag) in the next water routine. Sources of calcium = calcite, calcium, oyster shell flour, gypsum (food grade). I avoid egg shells, they require some extra work despite what you will read. This will not harm the plant unlike cal/mag which will start killing the soil microbes. Not what we want.

^^^ that all said, hard to trouble shoot without a pic but it sounds like the ladies are growing fine and you have a few yellow leaves. I worry about insects (spots on leaves), and insects... did I mention I worry about insects?? In a soil grow you should have everything you need. I'd stop with the tabs whatever they are...You should be able to get to the end with the soil you have going.

Flushing?? Whats that?

Read about Cation exchange here you don't have enough water to flush nutrients away without killing the plant first = fact. A hydro grow maybe but not a soil grow.

Cation exchange link - this debunks flushing soils:

Minerals are held onto in soil via cations and anions - positive and negative charges - water does nothing to either a positively or negatively charged mineral. This article also points at the negatives of having too much Mg in the soil. Since plants don't use or require much at all, adding in some extra Mg in most cases makes things worse for the soil and the plant.

Cation Exchange Capacity in Soils, Simplified


hmm, you're using ewc @ 25%. You're brave ( if you're using commercial variety). I've tested a few samples and they've been pretty high in Urea compounds. To the point I'd not use it beyond 5% of my grow medium. If it's working for you up until this point then perhaps you're using different stuff or you're DIY'ing it. Some Earthworm casting are being done via pig/ chicken manure we think. We've found high levels of Guanidine, Urea / Ammonium compounds in the bags. Great for mixing it with larger volumes of soil to dilute the excess nitrogenous compounds but not great for a smaller growing plant.

Use it with caution. Have it tested for urea, Ammonium and Nitrates before using it. If it is neutral then by all means go for it.
It's probably better to make your own which is pretty easy though it does take time.

Your suggestion about the tabs being too hot is probably more likely.

*I completely agree about the light btw. No way LED is going to cause issues with Ca/Mg. Not possible.
 
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