Effect of LED shoplights on tomato plants

rwsacto · March 17, 2016

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

KarenO · March 17, 2016

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

Ricky Shaw · March 17, 2016

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

Father'sDaughter · March 17, 2016

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.

Ricky Shaw · March 17, 2016

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.

JohnAtk · March 17, 2016

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

BackyardFarm · March 17, 2016

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

Ricky Shaw · March 17, 2016

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.

Worth1 · March 17, 2016

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

rwsacto · March 17, 2016

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

rwsacto · March 17, 2016

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

bower · March 17, 2016

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!!!!

PhilaGardener · March 17, 2016

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!

Dark Rumor · March 17, 2016

Will you show comparisons as they grow?

frankcar1965 · March 18, 2016

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.

March 17, 2016	#4
Father'sDaughter Tomatovillian™ Join Date: Nov 2011 Location: MA/NH Border Posts: 4,917	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.

March 17, 2016	#6
JohnAtk Tomatovillian™ Join Date: Jun 2014 Location: London Posts: 10	What caused the yellowish ends of leaves of the plants in the left group? __________________ I am a Fantastic Gardener. ))))

March 17, 2016	#2
KarenO Tomatovillian™ Join Date: Oct 2012 Location: Vancouver Island Posts: 5,922	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

March 17, 2016	#3
Ricky Shaw Tomatovillian™ Join Date: Aug 2015 Location: Zone 6a Denver North Metro Posts: 1,910	My observation is: I'm buying an LED today.

March 17, 2016	#7
BackyardFarm Tomatovillian™ Join Date: Jul 2015 Location: Wisconsin, zone 4b Posts: 360	Oh interesting. I just was thinking about picking up an led to try. You may have just sold me on it!

March 17, 2016	#9
Worth1 Tomatovillian™ Join Date: Feb 2006 Location: Den of Drunken Fools Posts: 38,539	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

March 17, 2016	#11
rwsacto Tomatovillian™ Join Date: Sep 2010 Location: Sacramento CA Posts: 288	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

March 17, 2016	#12
bower Tomatovillian™ Join Date: Feb 2012 Location: Newfoundland, Canada Posts: 6,793	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!!!!

March 17, 2016	#13
PhilaGardener Tomatovillian™ Join Date: Jan 2014 Location: Near Philadelphia, PA Posts: 1,940	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!

March 17, 2016	#14
Dark Rumor Tomatovillian™ Join Date: Jan 2011 Location: Southeast Texas Posts: 287	Will you show comparisons as they grow?

March 18, 2016	#15
frankcar1965 Tomatovillian™ Join Date: Feb 2008 Location: NW Louisiana Posts: 89	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.