HLG 40 and baby seedlings?

does anyone on here have any experience using the HLG 40 quantom board (5000k)? particularly on baby seedlings from day 1? how close can this light be placed above seedlings (from the moment they break soil) without burning them? can it be used like CFL’s and be an inch away from the plants, or since it’s a more intense type of lighting does it need to be hung higher above the plants than CFL’s do and thus would maybe cause some stretching? wanting to use it for seedlings from day 1 and up until they outgrow solo cups and can be transplanted into their forever homes in my real veg tent but if this light is going to cause stretching I would rather use some CFL’s. thanks in advance for any help.

One for LED man @dbrn32

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try it 12" (30cm) above the tops,
u will quickly know if this is too high or low.!

I was going to do that but I haven’t started any seeds yet :stuck_out_tongue: I’m finishing up my current grow first which is why I was just looking for anyone with experience/knowledge about them as I can’t do the testing/trial & error myself right now to find the answer myself.

there is not going to be a set height,
too many variables like temps, rh, plant strain, media, fert’s…

let the plants ‘tell’ u what they like and dislike,
with everything we do, plant observation is the most important.!
always watch your plants, even if there r no known changes.!!

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that’s very true I do agree with you 100% I was just more-so wanting a general idea /guesstimate as to how close these boards can go to the plants (at seedling stage) rather than a one number set height type deal ya know? I always adjust when needed in my grows I’ve just never grown a plant from seed/day 1 while using one of these boards before, I’ve only vegged with them after the seedling stage was already over so I honestly didn’t even know if it’s possible to use one of these boards on a seedling as young as 1 day old without the light being a mile away from them.

i would turn on the QB40 as soon as they break ground hung at 18" above the cups and see how they do, after their first single leaves start i’d drop it down some and see how they liked it.

thanks man :stuck_out_tongue: that’s what I’ll do when the time comes to pop more seeds. you’re very right though, one persons light height might work for them and their strain but end up not working at all for me and my strain I’m growing. so I will for sure have to figure it out myself regardless of advice given. 18" sounds like a very safe start for sure though, I’ll start there and slowly lower as/if I notice stretching :slight_smile:


knowing u r using a QB40 for veg, sounds like u have a perpetual grow going,

got any pics.?

here is my home made stealth perpetual grow box,
veg, moms, clones, seedlings on the right, bloom room on the left…

dry box and mechanical room up top…


I honestly haven’t used this QB40 yet, I bought it to use as a seedling/clone light to be used in a small grow box I was going to build because my normal veg tent is always full. I currently do my real vegging and flowering in a 4x4 tent with 2 QB260’s. I plan to buy 2 more 260’s and another tent for a flower room in the near future. no perpetual grow yet but that is my plan. haven’t taken any pics yet but I do plan on starting a journal next grow. I’m new to growing indoors I started about 6 months ago. that’s a very nice setup you got going. I hope I can get mine going like that soon.

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I would run it like a small t5 fixture. Start at 12" and adjust based on what plants tell you.


Where did you get those white pots

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thank you. I’ll try that out.

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they too r home made octo-pots,
made from aluminum trim coil and measure 5.5" across and 7.5" tall,
here is one next to a 1 gal nursery pot, 16 oz solo, and a clear 9 oz cup…