Lighting Light stress under 2VL, how to toughen up these plants?

[Animatey]

Hey Guys,

I'm still trying to learn how to use this light and having some issues.

I'm using timber grow lights 2vl.

I have to run this light as dim as possible and 14 inches from canopy or my plants get stressed.

Plants are currently 19 days old, and they look good (no defs, green but not too green, and about the right size). Seeing the tiniest bit of mag def on one plant.

They are in 4 inch rockwool cubes, and all indica varieties.

At current settings I measure LUX at canopy at a little more than 5k, which gives an estimated PPFD of only 75...

If I get up to LUX of 10k (slowly adding 2k lux a day by adjusting the dimmer) which is only about 150 PPFD I see some mild drooping, and a couple of them droop pretty hard an hour or two before lights out.

Roots are bright white and fuzzy, and I weigh my cubes on a digital scale before watering them to ensure I'm not overwatering. I let them get to 25-30% of their saturated weight before watering.

I'm only at an EC of 1.0 right now, and I started them at an EC of .5

The leaves are a little wavy, and this was worse when they were seedlings which I read is also light stress possibly.

The nodes have like no spacing between them. I'm limited on vertical height, but the sales person told me that a dimmer should make it work OK. I have removed the reflectors.

So... my plants look OK, but I'm worried that the yield will be bad if I can't get them taking more light... Any ideas?

 

[Animatey]

I can't edit the post for some reason, but I want to add that at 5k lux they look fine, they are not stretching, they are not drooping, growth is at a reasonable pace, but I just cannot imagine they will yield anything if I can't get to a higher ppfd...

 

[Animatey]

Quick update, my plan after talking to timber grow lights via chat is to just go really slow with adjusting the intensity upward. I'm going to try to max out at about 40k lux at canopy which is about 600PPFD which should be enough for me in my tiny little 2x1x3 grow cabinet...

I'm going to try to go 2k lux every day or so, stopping if I see anymore stress. It seems like they can take an increase one day, but then need another day to photoacclimate. So I will increase 2k, then next day rest, then increase 2k... until I am at 40k at canopy.

 

[Boradan]

as a rough guide:
Seedling: 50-150 ppfd
veg: 200-450 ppfd
flower: 500-800 ppfd

Of course, this varies from strain to strain, and even plant to plant of the same strain, but it is a ballpark figure.
It also depends on your light cycle. Longer daylight hours need less intense light (DLI - Daily Light Integral)
https://www.extension.purdue.edu/extmedia/ho/ho-238-w.pdf

You cannot FORCE the plant to accept a higher ppfd than it needs/can take. The ppfd that it can stand will increase as the plant gets older/bigger (to a certain point).
What you are trying to do by forcing more ppfd is the equivalent of trying to give a 1 month old baby the same calories per day as a fully grown adult.

 

[Animatey]

as a rough guide:
Seedling: 50-150 ppfd
veg: 200-450 ppfd
flower: 500-800 ppfd

Of course, this varies from strain to strain, and even plant to plant of the same strain, but it is a ballpark figure.
It also depends on your light cycle. Longer daylight hours need less intense light (DLI - Daily Light Integral)
https://www.extension.purdue.edu/extmedia/ho/ho-238-w.pdf

You cannot FORCE the plant to accept a higher ppfd than it needs/can take. The ppfd that it can stand will increase as the plant gets older/bigger (to a certain point).
What you are trying to do by forcing more ppfd is the equivalent of trying to give a 1 month old baby the same calories per day as a fully grown adult.

Hey man, thanks for the info!

I have messed up enough plants to know that I cannot force them to do anything

I was struggling to get them to be happy at 75pfd, and I wouldn't consider them seedlings anymore so that got me worried I was missing something. My best guess at this point is that I stressed them out early on with too much light and they are slowly recovering.

This is my first run with COB and it is definitely pretty different. I cannot believe how squat these plants are with (what appears to my eyes to be) so little light.

Limited vertical height is kicking my ass, but I do think the dimmer will allow me to finish the crop.

I'm going through the pdf you posted now, thanks again!

 

[Animatey]

Today is day 20 and they are actually looking OK today.
Light is about 12 inches above canopy, dimmed almost to minimum.