Stretching seedlings. Light distance for LED in seedling stage

R

RookieMuffin

Well-Known Member
Hi

Last grow I used a new LED light in my setup and I was giving my plants too much light which resulted in light stress. I'm new to the LED light so it takes some time to dial it in.

This time I went slow on the seedlings and started low.

It's a 100W LED. I don't have a par meter right now.

The manufacteurer recommends for seedlings 22 inches (55 cm) above canopy and 20-40% light power.

I did not want them to become light stressed again so I was hanging the light at 35 inches (90 cm) and power to 20%.

Plant stretched. So I lowered it 30 inches (75 cm) and 20% power.

Plant stretched again. So I increased the power to 30% and height was the same at 30 inches.

Again the plant stretches... So I've increased it to 40% still at the 30 inches height mark.

Then I started to research but it's hard to find how people hang the lights. I've found a list recommending for 200W LED hanging at 12 inches (30 cm) which sounds a lot to me.

So after researching I've lowered the light to about 24 inches (60 cm) and power 40% (40 watts).

I don't know if they will stretch again because it's not long ago I've changed it...

But how would you hang your LED? I can dim from 10-100%.

I don't know if the manufacteurer recommendation will work but at first I thought it may be too much light but now since the plant was stretching I think it might work. But what if the plant is still stretching?

It's ok if I have a little stretch this run but soon I want them to be squat when I've dialed in my setup. Maybe someone of you can help me and give me some recommendations or numbers they use (light power LED + height).

The seedling is almost 2 inches heigh... I think she could have been a little bit smaller with less of a stretch. But since I've light stressed them the last time I try to be careful now with the new LED lol.

I also have a small fan blowing on the seedling to toughen it up... Could that be cause of the stretching too? I always blow at my seedlings without stress but idk... maybe that could stress them to so they stretch?
 
simpleleaf

simpleleaf

Well-Known Member
I think you're doing fine, lowering and increasing intensity until stretch stops. I keep my lights between 24 and 12 inches. I have older LEDs which don't have variable power.
 
R

RookieMuffin

Well-Known Member
simpleleaf said:
I think you're doing fine, lowering and increasing intensity until stretch stops. I keep my lights between 24 and 12 inches. I have older LEDs which don't have variable power.
Click to expand...
Thanks for your answer! How much watt does your LED have?

So I will go on doing what I do until I have it dialed in...
 
R

RookieMuffin

Well-Known Member
MickFoster said:
I have found that a t5 works best for seedlings........3" above the top of the seedling and no stretch.........plants love the t5 light.
Click to expand...
So maybe I should buy one of these if I don't get it under control... Seedling T5 and Veg LED... Will think about that based on my outcome this time... Thank you
 
R

RookieMuffin

Well-Known Member
smokey0418 said:
Yes I do.

I use a spoton quantum meter and set for 300.

I would run 300 -350 all the way up until flower.

Plants seem to grow the best for me at this rate.

Enjoy and good luck with your grow.
Click to expand...
Thank you very much!

Even seedlings can take 300-350 PPFD? Wow thank you!

And how high do you go in flower?
 
rkymtnman

rkymtnman

Well-Known Member
if you are gonna dim it down, just give them a few hours dark. i've tried 6/2 for a few runs and they like that too.

try a bunch of different ways and see what you like.
 
R

RookieMuffin

Well-Known Member
rkymtnman said:
if you are gonna dim it down, just give them a few hours dark. i've tried 6/2 for a few runs and they like that too.

try a bunch of different ways and see what you like.
Click to expand...
Thank you for your answer!

I've never heard of 6/2 but sounds interesting! Will look into that thank you!
 
jimihendrix1

jimihendrix1

Well-Known Member
RookieMuffin said:
Thank you very much!

Even seedlings can take 300-350 PPFD? Wow thank you!

And how high do you go in flower?
Click to expand...

At the equator the PPF is 2000umol. So seedlings at the equator are regularly exposed to 2000umol. And at high altitude, its even more.

Ive used 1000w HID since they came out in the 70s for everything from Seedlings - Flowering. I also veg on 24/0, unless Im trying to slow them down.

I found no downside. I did switch from 1000w Metal Halide to Hortilux HPS when they mixed in a bit of Blue in the 90s I believe it was. I do have really really good outside air exchange. And there is no added CO2 at the equator. I believe the main thing to using high umol is air exchange, if not using CO2.


2000 µmol/m 2 /sec
At the equator, the sun’s intensity gives us a Photosynthetic Photon Flux (PPF) of 2000 µmol/m 2 /sec of light, which is roughly equivalent to 10,200 foot candles or 108,000 lux.
 
smokey0418

smokey0418

Well-Known Member
RookieMuffin said:
Thank you very much!

Even seedlings can take 300-350 PPFD? Wow thank you!

And how high do you go in flower?
Click to expand...
I would also run 18/6 and as mentioned you would adjust your dli if there tired lookin.

In flower I would like to push 9-1000 at the tops.
This would be a gradual transition but once there’s something worthy on there I’m pushing.
This is not plug and play hps.

Good luck with your grow.
 
curious2garden

curious2garden

Well-Known Mod
Staff member
1682394941364.png
RookieMuffin said:
Hi

Last grow I used a new LED light in my setup and I was giving my plants too much light which resulted in light stress. I'm new to the LED light so it takes some time to dial it in.

This time I went slow on the seedlings and started low.

It's a 100W LED. I don't have a par meter right now.

The manufacteurer recommends for seedlings 22 inches (55 cm) above canopy and 20-40% light power.

I did not want them to become light stressed again so I was hanging the light at 35 inches (90 cm) and power to 20%.

Plant stretched. So I lowered it 30 inches (75 cm) and 20% power.

Plant stretched again. So I increased the power to 30% and height was the same at 30 inches.

Again the plant stretches... So I've increased it to 40% still at the 30 inches height mark.

Then I started to research but it's hard to find how people hang the lights. I've found a list recommending for 200W LED hanging at 12 inches (30 cm) which sounds a lot to me.

So after researching I've lowered the light to about 24 inches (60 cm) and power 40% (40 watts).

I don't know if they will stretch again because it's not long ago I've changed it...

But how would you hang your LED? I can dim from 10-100%.

I don't know if the manufacteurer recommendation will work but at first I thought it may be too much light but now since the plant was stretching I think it might work. But what if the plant is still stretching?

It's ok if I have a little stretch this run but soon I want them to be squat when I've dialed in my setup. Maybe someone of you can help me and give me some recommendations or numbers they use (light power LED + height).

The seedling is almost 2 inches heigh... I think she could have been a little bit smaller with less of a stretch. But since I've light stressed them the last time I try to be careful now with the new LED lol.

I also have a small fan blowing on the seedling to toughen it up... Could that be cause of the stretching too? I always blow at my seedlings without stress but idk... maybe that could stress them to so they stretch?
Click to expand...
1682394941364.png
These are 3-4 days old. They are 24" away from an HLG 250W Veg Pro dimmed to 10%, no stretch. My PPFD is 263 at their canopy height.
 
DoubleAtotheRON

DoubleAtotheRON

Well-Known Member
You just have to adjust accordingly. Every strain/pheno is different. Some will stretch no matter the manipulation in light. After cross breeding this plant for decades, there has been a DNA drift.... nothing is as stable as it was 100, or 1000 years ago. Same thing as humans. The human race was once pretty stable outside of disease. Now, we have defects and mutations. I've had the same strain, but different phenos do fine, but the phenos are completely different...I had one pheno from a mother (5 babies) that just died mid flower from the same mother (never finished the mother), but they were all from M5 of that strain. I try to explain it like this. You have 2 parents that have 12 kids... are they all going to be identical?.. no. Some are going to to be short and fat, some skinny and tall, some retarded, some smart (good structure), or just die..... just like humans. This is why pheno hunting is important these days. You want to find that one kid from the parents that is smart, structurally sound, healthy, gets a PHD and becomes a brain surgeon, and clone her.
 
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