LED Watts /sq ft - feedback on the lumen overload

[belacttu]

I've found information about this all over the internet, but I wanted to kind of get feedback from the marijuana community in particular since your feedback is more important than someone growing - strawberries, per say. It's related to light = yield. I'm curious about adding lights, simply to increase yield. But this is only my third grow over ten years, and the first in five. Back then, I used MH and HPS bulbs. I'm still learning the numbers and evolution of teach.

The general consensus seems to be 30-35 watts per square foot is ideal for LED growing. I have an efficient multispectrum LED that pushes 260W true watts.
In a 2x3 tent, you have 6 square ft to work with which means an average of 43W per square foot. 3 plants can get a comfortable 2 square ft each and have more than enough recommended light.

Now, knowing that I have what should be enough and then some for four plants, adding another light of the exact same model would be pure overkill. Since I would only need 210-240w for the recommended medium and I pump out 260w, adding another light to the equation and changing nothing else gives me 86w per square ft. While I've heard many times over to crank the lumens, especially when flowering, I don't want to overdo it.

Is there "too much" light for an area? Would say, 100W per square ft for 4 plants increase their yield, or harm them? Is there a sweet spot that is a "if you have a way to get to it..." number? Have you added overkill lights during flowering and have you noticed a difference? Or nothing really noticeable? Unlike times before, I had the finances to buy a much better set up this go and could add more. 2x3 is just all the space at home I have to work with. Of course when I talk about increasing light output, I entirely am aware of and am considering the extra heat output and also being able to be controlled. This is just a question of more lights in a "perfect scenario".

 

[Rocket Soul]

When you hit around 40w/foot of modern efficient led you really need to step up your game re everything else in your grow: perfect environment and ideally hydro. It gets harder and harder to get the plant to keep up with light levels and it tends to get deficient easily. I doubt adding more light to your setup is going to change things unless your light is oldish (multispectrum? Blurple?).

 

[dbz]

I've found information about this all over the internet, but I wanted to kind of get feedback from the marijuana community in particular since your feedback is more important than someone growing - strawberries, per say. It's related to light = yield. I'm curious about adding lights, simply to increase yield. But this is only my third grow over ten years, and the first in five. Back then, I used MH and HPS bulbs. I'm still learning the numbers and evolution of teach.

The general consensus seems to be 30-35 watts per square foot is ideal for LED growing. I have an efficient multispectrum LED that pushes 260W true watts.
In a 2x3 tent, you have 6 square ft to work with which means an average of 43W per square foot. 3 plants can get a comfortable 2 square ft each and have more than enough recommended light.

Now, knowing that I have what should be enough and then some for four plants, adding another light of the exact same model would be pure overkill. Since I would only need 210-240w for the recommended medium and I pump out 260w, adding another light to the equation and changing nothing else gives me 86w per square ft. While I've heard many times over to crank the lumens, especially when flowering, I don't want to overdo it.

Is there "too much" light for an area? Would say, 100W per square ft for 4 plants increase their yield, or harm them? Is there a sweet spot that is a "if you have a way to get to it..." number? Have you added overkill lights during flowering and have you noticed a difference? Or nothing really noticeable? Unlike times before, I had the finances to buy a much better set up this go and could add more. 2x3 is just all the space at home I have to work with. Of course when I talk about increasing light output, I entirely am aware of and am considering the extra heat output and also being able to be controlled. This is just a question of more lights in a "perfect scenario".

@Rocket Soul got ya. Once you start exceeding 40 watts per sq foot with decent leds you need to be running sealed, co2 and really dialing in environment otherwise the plants won't be able to use all of the available light and may burn instead. 100 watts per sq ft is extremely excessive even with co2 imo.

 

[Bookush34]

my 3x3 has the potential to crazy over load with light. Which I have done.
I have 905watts or COBs.
That puts me at 100watt/sqft.


I have been using dimmers and a light meter to set my canopy at 1000 PPFD. And with 12 cobs it’s a very even coverage.
the top 4 vero 29s I have been running cranked up and at 24-30” since I added the uv light. As it need that kinda plant distance
I am attempting to use the bar lights for side lighting where the main light starts to fade out.
This summer I am going to change my grow stuff around the have both tents in the same room. Hoping to step up to a 4x4 for flowering.

that would put me in the 55watt/sqft area.

 

[DukeFluke]

Is there a sweet spot

There's always a sweet spot and it's environment dependent. Your plants will show you what it is, so pay attention to them.

In veg, for example, if you notice the leaves doing anything other than praying upward and lush growth with that fountain effect from the top, then you're not in the sweet spot and the structure of the plant will be percentage points lower than if it were. That can be caused by the light being too close, even by a few inches.

Lower your extraction, raise the temps, raise humidity - usually just lowering extraction sorts that out in a tent - and start your lights full and high. Lower them gradually to the point where the plant stops looking super vigorous, then back up again to where it does the next day. That's your sweet spot.

In flower they manage better with much closer distances. My guess is it's to do with DLI and the reduced daylight hours and the longer down time to assimilate and recover. but whatever the reason, come 12/12, the LEDs can be almost touching with no ill effect.

 

[belacttu]

@Rocket Soul got ya. Once you start exceeding 40 watts per sq foot with decent leds you need to be running sealed, co2 and really dialing in environment otherwise the plants won't be able to use all of the available light and may burn instead. 100 watts per sq ft is extremely excessive even with co2 imo.

Okay so I wouldn't get more portent buds per say because it's harder for them to use that light energy?

 

[belacttu]

When you hit around 40w/foot of modern efficient led you really need to step up your game re everything else in your grow: perfect environment and ideally hydro. It gets harder and harder to get the plant to keep up with light levels and it tends to get deficient easily. I doubt adding more light to your setup is going to change things unless your light is oldish (multispectrum? Blurple?).

I have a full spectrum Mars, I've not heard the best things about the blurple

 

[Rocket Soul]

I have a full spectrum Mars, I've not heard the best things about the blurple

Adding more light: if you buy another grow light it would be to replacee your current light, dont buy another mars blurple. If you just want a cheaap wway to add a bit of light and spectrum id suggest you get some warm white led light bulbs in and take the plastic hood of: guetto solution. Try for something with around 130-140lum/w at least. Adding a bit white led fills in the spectrum where blurple is lacking.

 

[Southernontariogrower]

my light is 600w high powered led, in a 4x4, which is 37.5w per square ft and is plenty, they get about 1080 true umol 2ft s. 1484mol rated in sphere test, my light is Hydrotek if you want to look it up, it might give you an idea, it took my young plants 1 month old, 2 full weeks veg with light 2 plus feet away and 3rd week of flower till turned up full, was running about half power on potentiometer, for most of those weeks, they were under a 1000w se hps, hydrolux in cool tube at about 1.5 ft away. So they can be powerful. And spectrum really means alot. With leds you get what you pay for, I'd say between 1000-1500 for 4x4 but maybe 8 if diy, I might push for 750w for 4x4 next light I buy or make, would like, to do 5x5 so 1000w led which would be 40w sq ft

 

[Southernontariogrower]

my 3x3 has the potential to crazy over load with light. Which I have done.
I have 905watts or COBs.
That puts me at 100watt/sqft.


I have been using dimmers and a light meter to set my canopy at 1000 PPFD. And with 12 cobs it’s a very even coverage.
the top 4 vero 29s I have been running cranked up and at 24-30” since I added the uv light. As it need that kinda plant distance
I am attempting to use the bar lights for side lighting where the main light starts to fade out.
This summer I am going to change my grow stuff around the have both tents in the same room. Hoping to step up to a 4x4 for flowering.

that would put me in the 55watt/sqft area.





View attachment 4827023

Nice set up

 

[Southernontariogrower]

I'm at 90 degrees and about 70 rh but with heat rh seems good 16 inch fan, don't vent tent till lights out, suck co2 out at lights off, leave vent fan on till light on, if not rh is low and no pm means ok. Have vpd chart and was sticking too it on nose then someone told me about another vpd chart, and I had wrong one, apparently. Since it wasn't broke I didn't fix it, girls doing better than ever have, genetics helps.

 

[Southernontariogrower]

Nice set up

Cobs are way to go, can keep adding on, and if you run soft will last 15 years

 

[dbz]

I have a full spectrum Mars, I've not heard the best things about the blurple

In general most of them perform poorly compared to their counterparts

Okay so I wouldn't get more portent buds per say because it's harder for them to use that light energy?

Like many things it is a curve with diminishing returns on each side of "ideal" as is appropriate to your environment. If you use more light than the plant can utilize it can result in "light burn" or if the lights are too close. Of course there is also wasting needless electricity. Your plants can tell you how much light to use the numbers given you are just general approximations as each pheno may want a little different than another. However they are a decent guideline. There becomes a point considering all environmental conditions are optimal without CO2 that the most light the plant will process is x. If you add CO2 in a sealed setup then the plant can take a bit more, even then though it still becomes up to a point.