LED light bleached my vegging ladies

J

jonnynobody

Well-Known Member
I have 2 nursery tents. 1 had 2 150w LED's. 80-82 temp. The second tent has an 8 lamp 4' 320w T5. 80-83 temp range. The ladies under t5 look amazing as usual. The LED tent experienced some high temps about a week ago for several days topping 90 at one point during a hot stretch we had in Michigan.

I cut a new 6" duct hole to the outside and installed a louver so I could dump the hot air from the tents outside. I then installed a 15,000 BTU portable air conditioner and cut a 6" hole and installed another louver to dump the hot exhaust outside.

Heat problem solved, but some foliage did experience some minor light bleaching and leaf twisting. I removed the 2 LED units from the problem tent. I replaced those with 2 2' 8 lamp high output t5 units. 192w each. Less heat and more gentle on the ladies. Usually I run the LED units as side lighting in my flower room with 2 1000w hortilux's, but I'm installing a new spider farmer SF-4000 in there or a look alike I bought off Alibaba and I thought I would repurpose them for my veg tent. No sale on the repurposing. However, I have run these 2 LED units in my veg tent before with amazing results. That tent performed slightly better than the T5 tent.

I think the high intensity of the LED units coupled with a week of high temperatures is the culprit.

I will most likely buy another 320w 8 lamp hydrofarm T5. I paid $168 out the door for my last one. Bulbs once a year. Excellent results. Minimal heat. I like LED for flower. The fixtures are still too expensive to outfit my nurseries with them @$500 each to cover my 5x5. In another year or two when costs come down I'll pull that trigger.

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Light bleach pictures
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And pictures of the ladies in the T5 tent. Healthy, lush, and looking great.
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Often light intensity appears to be the problem when in reality the plants are having difficulty up taking nutrients for some reason, they get enough to handle the lower photosynthesis rates but not enough for the higher rates required by the more intense light. Generally it's either low PPM, pH is off or an excess one element is antagonizing another.
 
Renfro said:
Often light intensity appears to be the problem when in reality the plants are having difficulty up taking nutrients for some reason, they get enough to handle the lower photosynthesis rates but not enough for the higher rates required by the more intense light. Generally it's either low PPM, pH is off or an excess one element is antagonizing another.
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Could severe high temps contribute to a problem like that? That last heat wave we had I had highs of 90 in the problem tent for nearly a whole week before I cut another 6" hole and installed a louver to the outside to dump the hot air from the tents. I've never had this many lights and plants going during the summer and had to rethink my HVAC. I wound up putting a portable a/c in the same room as the 2 veg tents to keep temps at a constant 78-82 in both tents. Alas, the damage has been done. Ventilation is not to be taken lightly. I'll probably veg them another 1-2 weeks before I flower them so they get a good opportunity to lush up again. My theory is the high temps coupled with the LED light intensity stressed the ladies in the problem tent. Oddly the black widow just took it without issue. Lush and green. And that happens to be the smallest plant in that tent.
 
rkymtnman said:
Mg deficiency, not light bleaching.
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Normally I would agree, however both nursery tents receive the same fertilizer from the same reservoir at the same time. All of the plants are in the same medium in the same size buckets. Both nursery tents are hooked up to the same ventilation system. The only variable has been the heat and different lights. My other nursery tent with the t5 never exceeded 84. All of those plants look fantastic. No twisted leaves and no foliage damage.
 
Kassiopeija said:
well LED works best with higher temps aim for ~30°C
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That's true if you're running Co2 which is recommended. I am not running co2. Higher temps are no bueno for me.
I'm going to buy another 4' hydrofarm t5 for $176 on Amazon today. The performance is pretty sweet. I have 2 of the 2' 8 lamp T5's in there now @192w each, but they do not produce the same volume of light as the 8 lamp 4' T5 @ 432 watts. The variance seems marginal, but when you look into the tent visually it's quite significant. Gotta figure out what to do with these 2' t5's now. I've had them for over 5 years each. Good for a clone / seedling tent.
 
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ive always found that unless you're using very low power led's for vegging then you'll need a dimmer and work your way up slowly, especially if you dont have much headroom.
 
jonnynobody said:
That's true if you're running Co2 which is recommended. I am not running co2. Higher temps are no bueno for me.
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up to 30°C its still natural - as the sun outside emits alot of heat. Cooling of leaves drives transpiration, which increases CO2 intake. All a part of VPD, ofc ambient rH also chimes in here
 
jonnynobody said:
Thanks for the good info. I was really getting a little perplexed by it. It's been over a year since I've had an issue like this. I suppose I was due :)
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i add 1gram per gal of Epsom always.

i've used my well water for a few years now and my last grow was the first Ca defic i've had since then. weird how somethings you can get away with for awhile.
 
I am not a big fan of purple lights, because you don't actual know what wavelength they are. yeah most Chinese companies will tell you they are in the 400 to 450nm range, but most aren't, they are really in the 365 to 400nm range and that's not good for any plant and especially for a young plant as beaming light on a young plant in that range will always cause a truly human avoidable calcium deficiency, which makes the leaves look they have white blemishes wherever the led(s) with those wavelengths are directly beaming down onto the leaves. And young plants do try to compensate for that, but its hard for young plants to do that because even when a plant may live in the best 'wonder soil' there still won't ever be enough calcium for the plant to fix that kind of human avoidable calcium deficiency! Yeah, some wavelengths of light may look all cool n' shit, but in all reality they simply aren't good for young plants. Now when I am talking about purple lights, certain purple wavelengths (365 to 400nm), can actual reduce a young plants ability to uptake nitrogen by as much as 50%, so when a plants ability to take up the normal amounts of nitrogen it causes the pH range for both calcium and magnesium to be greatly narrowed which can cause one or both of those secondary nutrients to become locked out if the environments pH range is above or below the now narrowed pH ranges for optimal calcium and magnesium uptake which directly causes those white blemishes!
 
piratebug said:
I am not a big fan of purple lights, because you don't actual know what wavelength they are. yeah most Chinese companies will tell you they are in the 400 to 450nm range, but most aren't, they are really in the 365 to 400nm range and that's not good for any plant and especially for a young plant as beaming light on a young plant in that range will always cause a truly human avoidable calcium deficiency, which makes the leaves look they have white blemishes wherever the led(s) with those wavelengths are directly beaming down onto the leaves. And young plants do try to compensate for that, but its hard for young plants to do that because even when a plant may live in the best 'wonder soil' there still won't ever be enough calcium for the plant to fix that kind of human avoidable calcium deficiency! Yeah, some wavelengths of light may look all cool n' shit, but in all reality they simply aren't good for young plants. Now when I am talking about purple lights, certain purple wavelengths (365 to 400nm), can actual reduce a young plants ability to uptake nitrogen by as much as 50%, so when a plants ability to take up the normal amounts of nitrogen it causes the pH range for both calcium and magnesium to be greatly narrowed which can cause one or both of those secondary nutrients to become locked out if the environments pH range is above or below the now narrowed pH ranges for optimal calcium and magnesium uptake which directly causes those white blemishes!
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That's what I have. They are purple and reds. I had been using them as side lighting in my flower room, and maybe that's where they should stay if not completely eliminated from the garden. I have a couple of newer LED units on the way for my flower room. It looks like they're getting shelved or donated when my new units arrive. I think I'm going to stick to my high output hydrofarm T5 for my nurseries. They perform amazingly well and are dirt cheap. Vegging plants look happy as can be under that thing.
 
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