Noob LED question: what percentage light output for seedlings?

J

jashbery

Active Member
Hello there, it's been around 5 years since my last grow (which I used to do regularly, very basic 250 HPS setup). I'm starting a new grow, using the Mean Well HLG-120H-48B (my first time growing with LEDs), keeping it about 40cm above my seedlings, with the light dimmed to around 60% of capacity on the advice of shop staff. The seedlings look healthy but, compared to my previous grows, grow very slowly, with only two sets of leaves at day 11 of germination.

Is this normal for LEDs? Would you suggest I put the lights on at 80 or even 100% at this stage, or is patience the key ingredient here? I ask only because previous experience set me up to expect a seedling at least twice this size at this stage.

Growing in coco coir, seeds are auto-fems (Copenhagen Kush) with most recent nutrient solution set at .9 EC, ph at 5.7.
with thanks,
Jash
 

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SofaKingHigh_

SofaKingHigh_

Well-Known Member
jashbery said:
Hello there, it's been around 5 years since my last grow (which I used to do regularly, very basic 250 HPS setup). I'm starting a new grow, using the Mean Well HLG-120H-48B (my first time growing with LEDs), keeping it about 40cm above my seedlings, with the light dimmed to around 60% of capacity on the advice of shop staff. The seedlings look healthy but, compared to my previous grows, grow very slowly, with only two sets of leaves at day 11 of germination.

Is this normal for LEDs? Would you suggest I put the lights on at 80 or even 100% at this stage, or is patience the key ingredient here? I ask only because previous experience set me up to expect a seedling at least twice this size at this stage.

Growing in coco coir, seeds are auto-fems (Copenhagen Kush) with most recent nutrient solution set at .9 EC, ph at 5.7.
with thanks,
Jash
Click to expand...
Might be genetics but probably just patience is needed
 
J

jashbery

Active Member
Thanks SofaKingHigh, but here we are now at 16 days since germination and it's still a little runt. From previous experience using 250 HPS and the same strain, this plant should be twice the size, no? EC is now up to 1.1. I'll give it another week or so before admitting defeat unless you have any other advice? Nutes are Canna Coco A and B, not using any supplements (as in previous successful grows).

Have other growers experienced longer veg times with LEDs compared to HPS?
 

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Rocket Soul

Rocket Soul

Well-Known Member
OP: what environment are you running for your seedling? Do you follow VPD? Plant looks a bit pale which could mean over lighting or that it doesnt get enough nutes. With leds you really have to dial in transpiration thru climate/vpd; no transpiration no nutes. The easiest thing to try would be adding a bit of heat unless its real hot in there.
 
Ezleaves

Ezleaves

Member
jashbery said:
Hello there, it's been around 5 years since my last grow (which I used to do regularly, very basic 250 HPS setup). I'm starting a new grow, using the Mean Well HLG-120H-48B (my first time growing with LEDs), keeping it about 40cm above my seedlings, with the light dimmed to around 60% of capacity on the advice of shop staff. The seedlings look healthy but, compared to my previous grows, grow very slowly, with only two sets of leaves at day 11 of germination.

Is this normal for LEDs? Would you suggest I put the lights on at 80 or even 100% at this stage, or is patience the key ingredient here? I ask only because previous experience set me up to expect a seedling at least twice this size at this stage.

Growing in coco coir, seeds are auto-fems (Copenhagen Kush) with most recent nutrient solution set at .9 EC, ph at 5.7.
with thanks,
Jash
Click to expand...
Maybe over saturating the Rockwool?
 
J

jashbery

Active Member
Rocket Soul said:
OP: what environment are you running for your seedling? Do you follow VPD? Plant looks a bit pale which could mean over lighting or that it doesnt get enough nutes. With leds you really have to dial in transpiration thru climate/vpd; no transpiration no nutes. The easiest thing to try would be adding a bit of heat unless its real hot in there.
Click to expand...
Thanks Rocket Soul, I'll be honest with you, I didn't even know what VPD was until you mentioned it and I looked it up! I'm running an oscilatting fan and inline/exhaust fan in a Diamond Box 80X80X160, Cornwall carbon filter kit 100mm/187m3, Mean Well HLG-120H-48B (my first time growing with LEDs), now keeping it about 60cm to ensure I'm not over lighting. EC is 1.1 now, thinking of raising it a bit. What do you think? I mean, I've done lots of grows in the past, albeit with a 250 HPS, not LED, and never seen such slow and, as you note, pale development before.

Temps by the way are around 77 C.

best and thanks again,
Jash
 
Rocket Soul

Rocket Soul

Well-Known Member
Ezleaves said:
Maybe over saturating the Rockwool?
Click to expand...
This was my second thought but i dont know rockwool to well; is it a good idea to plant a rockwool cube into coco/soil? Not sure.

OP: you have a somewhat purple stem which is usually not a good sign, too much light with too little heat usually
 
C

cage

Well-Known Member
jashbery said:
Thanks SofaKingHigh, but here we are now at 16 days since germination and it's still a little runt. From previous experience using 250 HPS and the same strain, this plant should be twice the size, no? EC is now up to 1.1. I'll give it another week or so before admitting defeat unless you have any other advice? Nutes are Canna Coco A and B, not using any supplements (as in previous successful grows).

Have other growers experienced longer veg times with LEDs compared to HPS?
Click to expand...
Comparing to your 250W HPS you are using less light and you have considerably less heat from the light.
Especially the heat could be a factor here.
For so young plants the root growth speed translates into faster grow speed after small delay.
If there's not enough root system to support higher amount of light, any extra light will not help.

Medium quality also contributes heavily into root growth speed, properly moist yet oxygen rich enviroment will promote vigorous root growth.
 
J

jashbery

Active Member
PS - as the plant is still in seedling stage, the exhaust fan is timed to exhaust the tent every other hour so I can build up a little humidity. Once it starts flowering (assuming it does!) I then switch it on 24/7.
 
J

jashbery

Active Member
Rocket Soul said:
This was my second thought but i dont know rockwool to well; is it a good idea to plant a rockwool cube into coco/soil? Not sure.

OP: you have a somewhat purple stem which is usually not a good sign, too much light with too little heat usually
Click to expand...
Thanks Rocket Soul and EZ Leaves, I've used rockwool in coco at least 5 or 6 times in the past, and never had an issue. As this is my first time growing with LEDs, I figured the LED was the culprit. Very mysterious! Temps are generally around 77 C, which I always understood was pretty ideal?
 
Rocket Soul

Rocket Soul

Well-Known Member
jashbery said:
Thanks Rocket Soul and EZ Leaves, I've used rockwool in coco at least 5 or 6 times in the past, and never had an issue. As this is my first time growing with LEDs, I figured the LED was the culprit. Very mysterious! Temps are generally around 77 C, which I always understood was pretty ideal?
Click to expand...
You must mean 77F right? 77C is a lot too much. If you can bring 77F up a bit and stay high humidity youd probably see better growth.
Check out vpdchart.com
 
J

jashbery

Active Member
Rocket Soul said:
You must mean 77F right? 77C is a lot too much. If you can bring 77F up a bit and stay high humidity youd probably see better growth.
Check out vpdchart.com
Click to expand...
D'oh! Yes, F, not C! I'll see what I can do about raising the heat.

Thanks to everyone for your advice and input!
 
J

joesoap2013

Well-Known Member
Hps the tent bes cooler I would never have liked my tent near 25 degrees you would have to raise the light up
The leaves loves the heat
Harder to train but I'm a real noob at led
But one of my first things ..I'd call the plants dumb
They seem happy to sit under a big fan leaf in the shade
Must be the lack of blue in the hps makes the branch's stretch
Them big stupid 125 and 250 cfl bulbs the branches would have clung to the stem
 
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