Effect of LED shoplights on tomato plants
 

I purchased two LED shoplights for the garage but set them up as grow lights for tomato season. Tomato plants were potted up at second true leaves. The tray on the left was placed under the LED lights for about two weeks. The tray on the right was under T12 and CFL lamps for the same 2 weeks. Both were raised in 50-70 deg temps.

The plant leaves under the LED lights are visibly more bluegreen with dark stems and more purple underneath. Otherwise they appear the same for size and vigor.
A few LED plants had mottled yellow on some leaves in the third photo.

From now on, the trays will be rotated, mostly under the fluorescent lights, until set outside.

Any observations or comments are welcome. Again, these are 4 ft. white LED shoplights ($25 at Costco), not LED growlights.

Rick

interesting comparison. I think they will all do fine and the colour will become the same in full spectrum sunlight. For vegetative growth of seedlings only, without expectation of flowering and fruiting, either LED or fluorescent will do the job quite well and expensive lights/fixtures are not needed. I have always used ordinary daylight tubes in cheap ballast fixtures for seedlings with success and minimal cost.
They look good. nice job. Time to pot up or plant out soon?

Karen

My observation is: I'm buying an LED today.

Effect of LED shoplights on tomato plants
 

I'm thinking the LED plants look like they were grown in a colder environment. I know my T8 fluorescent lights do generate some heat and keep the plants a bit warmer. I'm betting the LEDs produce little to no heat.

The color difference won't matter in the long run, but the stalks and canopy are plainly better on the LED plants. They all look pretty, very nice seedlings Rick.

What caused the yellowish ends of leaves of the plants in the left group?

Oh interesting. I just was thinking about picking up an led to try. You may have just sold me on it! :D

The leaf spacing is tighter, and it looks to me like a lot more sucker development on the LED plants. More pics?

I mean looking down in that first pic there's a big diff to me, look how much less of the white cups you see than the ones on the right.

I brought this up in another thread someplace and even with a link but I have no idea where.
Here is the rundown on LED lights as I know it and understand.

LED lights for people have 3 colors red green and blue.
We see them as white.
The (True) LED grow lights leave out the green as there is no need for it.
With huge indoor operations by leaving out the one LED light source you cut your utility bill by 1/3.

I was going to pick up the 100watt bright daylight 65K led at the store the other day but they were out.:(

Now will the poster please tell us what the color spectrum temperature was on the T-12, CFL, and LED lights were and what the energy consumption and output was on each one.

In other words the CFL lights have a consumption and equivalent wattage to an incandescent light.
A 23 watt CFL will be like or equivalent to a 100 watt light.
This is the amount of energy radiating from it in the form of light.


Worth

OK, poster here, :)

The fluorescent setup is 3-6500 k T12 tubes, one 3500 k tube and 8-warm white 23 watt CFLs, uses 307 watts including the small fan and can illuminate 3-1020 trays. The tubes and CFLs are several years old.

The 2-4 ft. LED fixtures draw 75 watts total and can illuminate 2 trays. I would guess the LED station, without fan, runs about 10-15 degrees cooler than the fluorescent with fan. The LED tubes are barely warm. These are FEIT LED fixtures. I have no info on the color temperature or CRI.

(Note: trays have been rotated between light sources in these latest photos)

I cannot account for the few yellowed leaves on the LED tray except they are all on the edges and may have received insufficient light.

Plant out here should start in about 2 weeks. The ground temp needs to come up about 10 degrees.

Rick

More info for those who want to know: ;)
FEIT 2 tube LED fixture is rated at 38 watts, luminous flux of 3700lm, and color temp of 4000K-B. The average temp of the tubes is 88 deg. F. (measured with laser thermometer)

The average temp of the T12 tubes is 86 in the center and 95 at the ends. The avg temp of the CFLs is 140 deg. F

Rick

The difference in the plants is pretty stunning. I agree it looks exactly like a temperature issue. :?!?: Very interesting!

The thing that got me, though, was the first statement.... "I bought these shoplights for the garage and then used them for tomatoes".... HAH!!!! :D:));)

The warmest part of the fluorescent shop light will be the ballast in the light housing. (The LED shoplight will not have a ballast.)

Really interesting comparisons, and it is great that the cost of the LEDs is coming down!

Will you show comparisons as they grow?

I posted earlier on the 'show me your seedlings' post about the led's I bought. Now that I have used them I have found similar results, they really seemed darker green than with fluorescents. I have always used 40 watts- four 2 tube fixtures for a total of eight tubes, I had them so I hated to throw them out. Then I got the two 100watt leds and so far I am really pleased. Both together were 44.00 on ebay. I have two fairly big shelves one still with the florescents but next year I will certainly switch over to leds completely.

A week later, all plants are mostly outside in the sun. The new growth on the LED plants is bright green, just like the fluorescent raised plants. The original LED leaves remain dark green and purple underneath. There is no observable difference in the size or vigor of the different plants.

Rick

The garden seems to be the great leveler of things. They were good looking seedlings, and the biggest takeaway for me is viability of LED in making seedlings. They put out so little heat they would seem a perfect fit for cold treatment techniques.
[URL="http://www.kdcomm.net/~tomato/Tomato/start.html"][/URL]

Many years ago when I was studying ecology and plant physiology, I learned that different shades of green represent slightly different (differently modified) photosynthetic pigments, which are optimal for different ecological niches, depending on the amount and quality of light. For example, the mosses and some other plants adapted to grow in the forest have chlorophyll pigments that are optimized to get the most efficient light capture in a shade situation.
Maybe tomatoes are able to adapt their pigments for different light regimes.

On the other hand, when there's a lot of purpling on the leaf, it may alter the shade of green that we perceive too.:?!?:
When I've put tomato plants outdoors here (much colder) some of them will completely lose their medium green tender greenhouse foliage in the first week or so. The new foliage is always tighter and a darker green, and is really rugged to the elements.
Don't know if the colour is from modified chlorophylls, other substances/pigments eg the purpling, or maybe due to slower growth, the pigment density is a variable too...???

Just some rambling thoughts. :surprised:

Thank you for sharing. Big difference.

This is the second season that I have grown some trays under LEDs. The color and stature of the LED trays is somewhat representative of your results. The antho expression and whatever other color pigments are elevated far above normal levels. Very dark drab green/purple on compact stout plants.

The stature may only have to do with the intensity that can be obtained at canopy level from an LED vs a regular FL setup.

Of possibly more importance, it has also been my experience that the root systems don't seem to develop at the same rate, with the LED lagging behind the florescents. That is an observation that has repeated a few times for me, but may be rooted in my setup and not the different lights.

[QUOTE=bower;545419]
Don't know if the colour is from modified chlorophylls, other substances/pigments eg the purpling, or maybe due to slower growth, the pigment density is a variable too...???
[/QUOTE]

The purple probably is due in large part to the accumulation of anthocyanin pigments, made as a protective response to high light levels (and perhaps the different spectrum of LED sources compared to fluorescents). It is possible that with LEDs you can leave a bit more distance between the plants and the light source and get the greener growth to which you are accustomed - LEDs are very directional in their light emission (to the point where making them more like traditional lighting sources is an engineering issue).

[QUOTE=PhilaGardener;547984]The purple probably is due in large part to the accumulation of anthocyanin pigments, made as a protective response to high light levels (and perhaps the different spectrum of LED sources compared to fluorescents). It is possible that with LEDs you can leave a bit more distance between the plants and the light source and get the greener growth to which you are accustomed - [COLOR=Red]LEDs are very directional in their light emission (to the point where making them more like traditional lighting sources is an engineering issue)[/COLOR].[/QUOTE]


They sell LED lights to take the place of regular lights in vesicles.
I am going to get some for my turn signals and brake lights for my motorcycle for the very reason you said that I put in red lettering in your post.
They are so bright that other drivers cant miss them. :lol:
I have seen these things in action.:shock:
Worth

I switched to LED after reading this thread, just after they sprouted. Plants are doing great and much cooler. Stays around 70 degrees.

So I went away for 8 days. I didn't know what to expect when I returned. I watered them good and left, hoping for the best. Any doubts about LED lights are gone! Crazy growth, especially Mortage Lifters on left. Those are 2 Lithonia single tube LED shop lights from HD. 1200 lumens each I believe

I have been looking at replacing the two short fluorescent lights units with one 4 ft. led. Any one have a preference? 6000 to 6500K for color. How many lumens are you going for?

Mmm. Careful about the color. If I understand it correctly, LEDs emit in a very narrow frequency band. Manufacturers mix LED colors to give the wider spectrum that plants like. If you are looking at a replacement tube you're probably okay.

As for rated color, I would go 6500K for a single lamp - closer to sunlight. For quad fluorescent, I mix two 6500K and two 4800K(?). But frankly, I don't think it's all that important.

.

[QUOTE=dmforcier;572560]Mmm. Careful about the color. If I understand it correctly, LEDs emit in a very narrow frequency band. Manufacturers mix LED colors to give the wider spectrum that plants like. If you are looking at a replacement tube you're probably okay.

As for rated color, I would go 6500K for a single lamp - closer to sunlight. For quad fluorescent, I mix two 6500K and two 4800K(?). But frankly, I don't think it's all that important.

.[/QUOTE]

This is why the (Grow) LED lights only emit in the red and blue spectrum and not in the green of middle spectrum.
This is why you see them looking purple.
This is not to say you cant use the ones made for us you just get light the plants dont need.
When they build the LED lights for human vision they mix all three spectrum's and we see it as white or yellowish light depending on what they use.

Speaking of this some guy was on a bicycle last night with a LED head light on his head.
It almost ran me off the road.:evil:

Worth

[QUOTE=rwsacto;542537]I purchased two LED shoplights for the garage but set them up as grow lights for tomato season. Tomato plants were potted up at second true leaves. The tray on the left was placed under the LED lights for about two weeks. The tray on the right was under T12 and CFL lamps for the same 2 weeks. Both were raised in 50-70 deg temps.

The plant leaves under the LED lights are visibly more bluegreen with dark stems and more purple underneath. Otherwise they appear the same for size and vigor.
A few LED plants had mottled yellow on some leaves in the third photo.

From now on, the trays will be rotated, mostly under the fluorescent lights, until set outside.

Any observations or comments are welcome. Again, these are 4 ft. white LED shoplights ($25 at Costco), not LED growlights.

Rick[/QUOTE]

Rick, We'd like to hear the end of the story. How did your Costco lit plants grow and produce once they grew up. Also the rest of you who tried the plain white LED shop lights.

This is an interesting topic, there is a lot of information/misinformation about different lights.

Best I can figure plants use blue and red for photosynthesis, but also other wavelengths as inputs for day length etc.

Commercial growers try and use blue and red leds because they line up on the photosynthesis bands and are very efficient.

White leds are less efficient and more expensive per unit of light output but have a good spectrum for growing.

This link is pretty informative about spectra and light levels vs flourescent.



[URL="http://www.carnivorousplants.org/howto/SoilsWater/Lighting.LED.php"]http://www.carnivorousplants.org/howto/SoilsWater/Lighting.LED.php[/URL]

[QUOTE=schill93;577877]Rick, We'd like to hear the end of the story. How did your Costco lit plants grow and produce once they grew up. Also the rest of you who tried the plain white LED shop lights.[/QUOTE]

They grew up fine and lived happily ever after:))

Once in the sun, there was no difference in new growth or roots compared to seedlings raised under fluorescents.

Rick

What are the varieties of tomatoes which underwent both treatments?