How close should I put LED shop light to seedlings?

[pointer80]

Hello all, I finally decided on 4 led shop lights that are 5000k and 4500 lumens for a total of 8 bulbs to raise up some mother plants. I have a question on how close to put them from the top of the seedlings? i have used T-12 shop lights to raise hundreds of veggie seedlings for the garden and normally hang them 2 inches or so above the seedlings but never used led shop lights before. Thanks all.

 

[Old Salt]

Start them about 18" from the seedlings. Move them closer if the plants get 'leggy,' and further away if you detect signs of light burn.

 

[pointer80]

Start them about 18" from the seedlings. Move them closer if the plants get 'leggy,' and further away if you detect signs of light burn.

thank you for the reply, Is the reason for this because led lights are that much stronger than the T-12's I have used for veggies and hung so close or is cannabis just more picky on light? Thanks

 

[TorturedSoul]

I'm interested in learning what you discover. I wouldn't think they'd be all that much stronger (if at all) in that form, since their wattage is probably significantly less than the fluorescent tubes that they're replacing. IOW, "the design goal" was probably to produce approximately the same amount of visible light (as far as our non-linear vision is concerned) with fewer watts. Possibly a little brighter, but not "exponentially" so.

On the other hand, I see warnings on every supplemental UV fluorescent tube that I look at, and they're low-wattage bulbs with maybe 10% of their output in the UV range. So... IDK, lol. With "discrete spectrum" lighting, one assumes the output will be concentrated among certain specific frequencies / frequency ranges, so its effects might mimic a higher-wattage light.

 

[Souptaco]

I started mine at 30 and dropped down to 22

 

[Bigjake8]

I have a couple 4100 led shop lights and I keep them 2 to 4 away haven't seen that they're better than the regular florescent but they keep them alive

 

[TorturedSoul]

I have a couple 4100 led shop lights and I keep them 2 to 4 away haven't seen that they're better than the regular florescent but they keep them alive

If you're able to maintan cannabis plants with them hung at a distance that's 24x to 48x the distance that people hang fluorescent shop lights above their plants, I'm guessing they must be at least a little better, lol.

 

[Bigjake8]

I meant inches not feet not enough coffee but yeah that would make a difference haha

 

[TorturedSoul]

....

!