Hello all,

My tomato seedlings underneath the LED lights seem slightly unhappy now. Please take a look at the photos. I'm not sure if it's because I had put the lights too close 18 in from the top of the plants at full power or if they might need some nutrition. There in three and a half inch pots and were planted around April 1st. I have raised the lights to about 2 ft above the plants and reduced power to 75%.

I'm still a newb at this, and I think in general your seedlings look better than mine which I planted out the other day, but they just look a little dry to me. You don't really seem to be getting much yellowing which is what I would associate with not enough nutrition, and they don't really look burned from the lights (I don't have adjustable LED's, but I had mine a lot closer than you do). You do have some close to the pepper plants that are very green but kind of shinier and curled--not sure if that is from being too close to the lights. If it was me I would water them with some liquid fertilizer, I have been using Neptune's Harvest Tomato & Veg, and also the Urban Farm/Texas Tomato Apples & Oranges (their recommendation for large seedlings, at least out of the choices I had), or their Flowers & Blooms.

If this is anything like one of my threads, you are going to get about 7 different opinions, so don't listen to me, at least until some more experienced members chime in.

The most likely cause of leaf troubles under LED lights is edema caused by the lack of UV and far red wavelengths. Some varieties are more sensitive than others, but in general LED is a difficult choice for tomatoes because they really do require these 'daylight' bits of the spectrum.
The physiological damage is caused by their inability to manage water flows - so some management techniques of the past, like allowing them to dry out completely before watering, are problematic. The sudden flow of excess water is taken up to the point of bursting cell walls, causing swellings and or scarring of tissues where cells have burst. Leaf curling as shown can be a reaction to the injury.
The best (and final) remedy for this is to get the plants out into daylight as soon as possible. Until you can do this, be very careful with your watering, that they don't get too much at one time. Moving back and reducing the light intensity was probably a good move, since it may have caused the plants to use up their water more quickly, thus becoming too dry, and then being unable to manage the water they received.

Bower wrote: ↑Sat May 07, 2022 7:04 am The most likely cause of leaf troubles under LED lights is edema caused by the lack of UV and far red wavelengths. Some varieties are more sensitive than others, but in general LED is a difficult choice for tomatoes because they really do require these 'daylight' bits of the spectrum.

I can't speak to what the far-red content of my 6500K T5HO fluorescents is, but I didn't see any appreciable difference this year between my ActiveGrow Sun White Pro LED's (0% UV, 2% far-red) and my other fixture with the fluorescents, other than the plants under the LED's were further along on flower development. I did have the LED's closer to the plants than the fluorescents, I don't know if that has anything to do with the flower production. The OP here is using a different style of LED and I also can't speak to the spectrum of that.

Now I'm wondering what kind of long term effects LED lights are going to have on people.
Like something they won't figure out for 50 to a 100 years even.

I had a horrible experience with LED lights one winter. They burned my tomato plants. The instructions said to put them 2" away, so I figured that was wrong, raised them to 8" or so, put another batch under them and they turned an odd colour and did not flourish .

Linda

worth1 wrote: ↑Sat May 07, 2022 7:58 am Now I'm wondering what kind of long term effects LED lights are going to have on people.
Like something they won't figure out for 50 to a 100 years even.

Not sure about long term, but i can speak from personal experience and say that in only a couple years of night shifts, my eyes got worse. When i finally went back to day light, my eyes got a little better, though not the same

For high intensity plant light LED's the users are cautioned to wear sunglasses. There is no doubt that it can and does affect our eyes at high intensity. The long term effects of less intense LED's are yet to be seen, except for the effects on the brain that are already known - like not being able to sleep after late night screen time. I wouldn't personally be happy if my plants were under lights that I needed to use sunglasses every time I walked into the room.

Thanks all. I noticed I had a similar problem last year with my eggplants and asked about it here! Anyway, I'll see how it goes with less intensity and more even watering. It would be a bit difficult to move the plants under the fluorescent lights in my shelves because they are close to being too tall for shelves.

I'll let you all know.

The lights in the professional grow rooms don't put out the white light as it is a waste of energy.
They wear some sort of red or pink looking glasses too due to the high intensity of the light.

worth1 wrote: ↑Sun May 08, 2022 8:21 am The lights in the professional grow rooms don't put out the white light as it is a waste of energy.

They seem to have just recently figured out that a balanced spectrum works better for plants. The higher quality led lights now have a mostly level spectrum curve.

Also, newer led lights are starting to come with uv and far red diodes built into the light. Far red has some fascinating research supporting it. Some people turn on the far reds before and after the light cycle to mimic the outdoor light spectrum at sunrise and sunset.

And regarding eyes, I think all grow lights are probably bad for one's eyes if exposed too much. A hat is a good idea when tending plants.