Ruderalis difficulties or environmental stress?

A question from a fellow grower:

Pure Coco, rinsed to a ph of 5.8, and pre-loaded with the General Hydroponics trio, at the rate for seedlings. The low rate.
Pro-Grow 260 watt LED. Both spectrum’s on, as I am finishing some Auto’s in the same space.
I started with it at 16". It is now 24" I’m trying to dial-in the best height. I will likely never use it for seedlings again, as a t-5 fixture in coming next month, for seedlings and clones. But, I still want to know what’s what with my LED. Never say never.
Temp is 29 C. Humidity runs from 25 to 50-ish.
24 hour light
3 in 1 gal pots, the other in slightly smaller Yogurt containers.
All have 1 1/2" rocks in the bottom of pots to aid in bottom drainage and aeration.

Here is what I am experiencing. 4 out of 6 's initial single, serrated leaves looked crispy on the outsides. Kind of splotchy white, like the chlorophyll was gone. Right after emerging. As emerging. After two days, this material was obviously dead, and I carefully trimmed it back to living tissue. The next set of leaves on all are coming on, and they look lime green, and healthy (with the exception of one with the very outer extremities of the pair white-ish. However, this is not moving in, it is staying the same. ) The Cotyledons are completely normal, and healthy.
Two of the girls look wonderful. As healthy as you please. Herein lies my perplexity. They have all been in the same environment. Identical. The obvious possibilities that came to my mind was 1) over fertilization. Seems unlikely, given that coco has 0 nutes in it. 2) light burn. I suppose there could be enough natural variation in the tissue of the different plants that the same amount of light good for two is to strong for 4. This, somehow, don’t seem correct, though. And the Cotyledons are unaffected. If it were light burn, wouldn’t they at least show some stress, under a magnifying glass? I think they would… 3) Something to do with the seeds themselves. Like the leaves were dried out prior to emerging??

I’m completely stumped here. It is the two perfectly healthy ones that make this almost impossible for me to land on one answer.
One last data point. I had them in the freezer, wrapped in 5 layers of airtight containment. I have kept my seeds in the freezer since Christ was a Corporal. Never once had an issue.

Any comments, criticisms or observations would be great appreciated

I never give seedlings nutrients. I believe that is the whole issue. However; You say new growth is good, so perhaps you can just move on to allowing them to grow a bit more.

Solved! In utter confusion, I decided to turn my slective switch LED to the grow only setting, and the ones with burnt leaves recovered in two days, and are now growing like crazy. So, the light, even at 24", was too strong for kids. I still am not comfortable with the one that didn’t show any ill effects. This doesn’t sit well with me, but, i suppose I can’t always figure out every puzzle. :wink:
Next time I pop beans it will be under T5’s, so I won’t have this problem in the future.
The take-away lesson? LED’s are deceptive, in that the light energy is much stronger than your eyes would let on.

BTW, these were normal, photo-period W.W., not Auto’s.

Why didn’t you post this query? I was surprised when you claimed it today.

So; for re: You went with the LED set up, instead of the Ipower? Just curious.

She already had the LED, apparently now we know why that LED has the different light settings that I was a little surprised and confused about, lol. Yes LEDs, especially the ones that do not include enough of all spectrum to appear white to our eyes, the strength can not be judged by our eyes, heck, near IR and IR spectrum and certain low level UV spectrum are good for the plants and may be included in some of the red light(IR) or blue light(UV). If it is a pure IR or UV LED bulb, it would look like no light was coming out at all to our eyes, but look at it through a digital camera and you may see a bright light coming from the LED. You might possibly be able to hold your hand an inch from the UV led and not feel anything but then have a little sunburn like spot on your hand later or you see no visible light come from the IR light but hold you hand near and feel a radiating warmth, almost like a heat lamp, coming from the lens. I’m surprised most name brand LED lights don’t come with better directions and information on exactly how they do work, what they are producing in light spectrum and recommended distances and such, maybe even some “do not” or, “no closer/smaller than” warnings, the only thing I’ve seen in some of my “professional” LED systems before I started “Frankensteining” my own was warnings to wear eye protection under the lights that included UV spectrum…

Another thing to think about with brightness and LED lights. The reason red lights are used by soldiers for reading maps in the dark, is red light – almost no matter how bright – does not register as bright to our eyes and it does not deplete night vision like other lights can.

Great point!!! Thanks. I’m now testing my theory. I popped the last similar bean I had, and we will see how it develops under the blue spectrum only. As I say above, I will be using, and always have used, Floro’s for starting beans/clones, but needs must, and it is interesting to know as much about one’s lighting system as possible.


Here’s the deal - the last bean I popped a week ago is happy as a clam under the blue spectrum, at a much closer distance than I had the light before. Down to 12 inches, I think. So…it was light burn. My theory is that the flower spectrum is much redder, and that end of the spectrum of light conveys more thermal emergy than the shorter wave-lenght end of the spectrum.

All the girls have recovered, and the burnt one have nearly caught up to the one that didn’t suffer burn. Phenomenal growth. I love my 3 watt LED’s. This began as an experiement, but I can’t see myself ever returning to HID lghting.

Latewood - don’t know how I missed your question above. I wanted to run this problem by Claire/Robert first, as a courtesy, and Claire said she had posted it before I could. So, it isn’t like I didn’t want to ‘own’ it.

Yes, even though more expensive to buy initially, I went with the Pro-Grow 260 light. From my research, I am convinced that they are the cutting edge of lighting technology. I love that I can work closely around them while on without having to worry about an exploding lamp from a stray drop of liquid. I love the almost complete lack of heat produced. I love not having a ballast. They are much lighter watt-for-watt. Much smaller for limited spaces. Cheaper to run (much cheaper). I couldn’t be happier. I’m going to buy another identical unit to fill out my 4x4 tent. One needs to be careful, as there are myriad cheap-shit LED’s, not worth the money they ask for them. And there are also ridiculously over priced, ‘top-end’ units, that don’t contain anything other than what the reasonably priced units are built from. Research, research, research.

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True that! Jodie, Amen, lol. LEDs are amazing when one understands how to use them. And your description of the LED market and prices is dead on!

Yes, Infrared is heat, most of the heat will be in the red LEDs. Infrared (infra means ‘below’ the red light on the spectrum), if any will be in the red LEDs and Ultraviolet (ultra means ‘above’ the violet or blue side of the spectrum) if any will be in the blue LEDs.

Another quick thought, there may be no real infrared anyway in your type of red LED, that would be specified by the more exact nanometer range, and yet still the red light is burning the leaves, but not really by heat as we know it. It just stimulates the chemical reaction in the chlorophyll too fast or too strong, if you will, and that results in more of a chemical like burn in the plant tissue. Well I guess, technically, all burns are chemical, rapid oxidization…

I’ll have to go to the woodshed, and think on this. I like the thought that it is not heat, per se, but rather the flowering spectrum is the catalyst for the burn-like damage. Good shootin’, Mac’.

Here are a couple very relevant links:’s-world-photosynthesis

It just dawned upon me that, for all I know, either the red or blue specrums might not overwhelm the seedlings, but taken together, they are too strong. Additionally, it seems intuitive that there could be many combinations of factors that might lead to desication of leaf material, not necessarily heat alone. I’m thinking here of ‘wearing out’ the cell structure of the leaf, by working it too hard. Or working it to hard for my low humidity environment. Too early to think well metaphorically, but you get the general idea, I hope.

I am facinated by the targeting of wavelenghts you get with an LED. Not wasting electricity creating energy that is mostly a problem (i.e. excess heat, light that doesn’t produce growth, but alarms the neighbors). I also read an article the other day on the size of diodes. Seems that three watts is the sweet-spot, given today’s technologies. Three’s are what my light is made from.

I think your thoughts are on the mark.

3 watt is what most of mine are as well, however so many companies are going to the 5 watt and there seems some evidence for better penetration, but the 5 watt haven’t been around as long and the 3 watt is more proven.

As it has been a couple years now since y’all had this conversation, have you reached any conclusions?

I understand researching information is very important, but unbiased opinions are hard to find. I’m finding that I can trust many opinions here in this forum, so I ask your opinion on this.