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Several months ago, I made the following experiment: Make a plant grow inside of a box with artifical lighting. I bought this lamp (15W):

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And removed the white sphere from it, so it got like:

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It burned my plant completly. After that, I bought several fluorescent lights and this experiment made me think that plants need to be far away from the lamps (at least 1m). This belief gave me some problems, I spent a lot of time with basil and lettuce never growing more than 1cm and never knew why because they weren't growing but several other plants were. Eventually, I decided to move them to very close my fluorescent lights and - to my surprise - the lamps didn't burn them plus, they are finally growing! See the following photo: That plant is very close to the lamp, ~2cm max and there are plants that even touch the lamp and don't get burned (This is a stand with 4 T5 54W each).

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As that plant is light hungry, I decided to make another experiment. I put another of it near a LED light, this time, I used the following:

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It's a 50W LED flood light. I put the plant at that distance (~10cm):

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And it got completely burned as you can see here:

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I have another experiment with fluorescent lights and the lights are VERY close to the plants, as in:

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And just as the other plants near the fluorescent lights, they don't get burned (that section of the leaf that looks burned is just because the leaf is old. The rest of the plant is completely fine). I measured the temperatures and got 40 degrees celsius in both fluorescent and LED flood light so it doesn't seems that it is heat that is killing them but then, what is? Can we adapt LED lights for plant growing with some filter similar to the filter I removed from the first lamp? I didn't test that lamp with filter but I will eventually.

NOTE: I know that there are lamps specialized for plants, I have some of them but I'd like to adapt standard LED lights because they are much cheaper.

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    There is a reason real grow lamps are more expensive than those little LED bulbs. The light emitted is heavy in the BLUE spectrum, not so good for animals. Plants will do just fine if your wattage is up quite a bit...I think 300 is minimum, height of the bulbs off the plants makes a difference, the type of soil you are using makes a huge difference (always use sterilized potting soil in ALL pots, not soil out of the yard). You are watering too much, not enough light and I don't see fans and air blowing...don't use fertilizer until you get decent lighting, potting soil, clean pots. – stormy Apr 20 '19 at 8:23
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    LEDs actually emit a ton of heat as they burn, and their overall performance depends on the ability of the LED to lose heat to the environment (this is why inexpensive LEDs today still warn not to put them in an enclosed light fixture). Here's an article that explains this in some technical detail. ledsmagazine.com/articles/2005/05/…. I've been growing seedlings under shop lights for 32 years with no issues. I do NOT, however, permanently grow under shop lights. IMO, that's what grow lights are for. – Jurp Apr 20 '19 at 12:39
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    Your "experimental procedure" seems rather faulty. LEDs close, burned, so rather than move LEDs away, put fluorescents far away, then close, then ignore prior LED burning and put LED close again without trying it further away. Try applying some basic logical thinking to your experimenting, but the fact is that you are dumping a lot of useless light at the plants (and burning a lot of useless power to do that) which a grow LED (much blue and red, no green) will do much more efficiently, wasting less of your money over time, unless you insist on always setting LEDs too close to the plants... – Ecnerwal Apr 23 '19 at 0:29
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    @Ecnerwal Not really. The LED is a light source. The fluorescent light is a light source. If one burns the plants, it's not unreasonable that the other could do that. The closeness on the LED'S in the second experiment is completely different and with a different plant. I don't see where the "logical thinking" is lacking. – Red Banana Apr 23 '19 at 11:38
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    @BillyRubina Don't mind Ecnerwal, in general, from my experience that person is just rude and is out to let everyone know about it. Honestly, Ecnerwal, this website would do just fine without your "contributions" maybe you should pick up coding and head over to the stack exchange, I think you would fit right in over there. – Rob Apr 23 '19 at 16:55

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