cbr shadow said:

I have a question regarding lights that I ordered today. After some research I decided on Spider Farmer SF 2000 LED lights. These are quantum boards, Samsung LED’s and a nice LED driver.
I see in all of the reviews that people put a minimum of 16-18” gap between the lights and the plant, which I believe is to avoid burning the plant. It looks like the center of the light at 18” will put PPFD near 900-1000 based on the reviews I’ve seen.
At 12:00 noon in the summer the sun puts out up to 1500 PPFD according to a study I read. Surely there’s no risk of burning plants on a summer day like this, correct? What am I missing?
I want to make sure I’m giving my plants everything they need for fast growth, but I’m confused about how close I should set the lamps above the plants based on the above.
My plants that I’m growing are Portulacaria Afra, which is a type of succulent/tree that loves sunlight. I’m growing these out for a bonsai project that I’m working on. These are inside a modular shelving unit that is 24”x60” footprint and is fully lined in mylar on the inside.
So my questions are:
1) How close should I put the lights to my plants? Everyone online says 18” but why not closer?
2) Why does the sun not burn plants at 1500 PPFD, but my LED’s will?
3) Should I get a PAR meter so I can test better?
4) Is sunlight always better than indoor lights, or is it possible to do better grows indoors than outside?

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Aqua Man said:

Because the sun does not provide 1500ppfd 18hrs a day.

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cbr shadow said:

I have a question regarding lights that I ordered today. After some research I decided on Spider Farmer SF 2000 LED lights. These are quantum boards, Samsung LED’s and a nice LED driver.
I see in all of the reviews that people put a minimum of 16-18” gap between the lights and the plant, which I believe is to avoid burning the plant. It looks like the center of the light at 18” will put PPFD near 900-1000 based on the reviews I’ve seen.
At 12:00 noon in the summer the sun puts out up to 1500 PPFD according to a study I read. Surely there’s no risk of burning plants on a summer day like this, correct? What am I missing?
I want to make sure I’m giving my plants everything they need for fast growth, but I’m confused about how close I should set the lamps above the plants based on the above.
My plants that I’m growing are Portulacaria Afra, which is a type of succulent/tree that loves sunlight. I’m growing these out for a bonsai project that I’m working on. These are inside a modular shelving unit that is 24”x60” footprint and is fully lined in mylar on the inside.
So my questions are:
1) How close should I put the lights to my plants? Everyone online says 18” but why not closer?
2) Why does the sun not burn plants at 1500 PPFD, but my LED’s will?
3) Should I get a PAR meter so I can test better?
4) Is sunlight always better than indoor lights, or is it possible to do better grows indoors than outside?

Click to expand...

cbr shadow said:

Good point! So it's technically possible to do better than the sun in a grow room/tent? Newbie questions here :-)

What PAR level can a plant typically take without burning? Do people here use a PAR meter to determine the best placement, or generally eyeball it?

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scyncegrown said:

1) You could go closer than 18" with that light, probably as close as 8" the main reason is to get your light to spread more evenly and not get hot spots.
2) The burn is from the heat from the light and not the light source also you have a more narrow band of wavelength with a grow light. 1500-2000 PPFD is common for the sun to put out and if you move a seedling into that to fast it too will burn.
3) Wouldn't worry about a PAR meter, anyone worth your time will be pricey
4) Sunlight is free and awesome for your plants, However the amount of control you get from indoor lighting can improve your overall growth. Especially if your plants are photo period sensitive like all the other plants on this site!

Check DLI charts on the area your plants are from and try to line your light up to best mimic the seasonal needs.

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Aqua Man said:

It will depend largely on the amount of IR a light provides. I would not recommend 8" at all. Even my v1 hlg 600 will cook plants at 12" no closer than 18" for me.

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cbr shadow said:

I have a question regarding lights that I ordered today. After some research I decided on Spider Farmer SF 2000 LED lights. These are quantum boards, Samsung LED’s and a nice LED driver.
I see in all of the reviews that people put a minimum of 16-18” gap between the lights and the plant, which I believe is to avoid burning the plant. It looks like the center of the light at 18” will put PPFD near 900-1000 based on the reviews I’ve seen.
At 12:00 noon in the summer the sun puts out up to 1500 PPFD according to a study I read. Surely there’s no risk of burning plants on a summer day like this, correct? What am I missing?
I want to make sure I’m giving my plants everything they need for fast growth, but I’m confused about how close I should set the lamps above the plants based on the above.
My plants that I’m growing are Portulacaria Afra, which is a type of succulent/tree that loves sunlight. I’m growing these out for a bonsai project that I’m working on. These are inside a modular shelving unit that is 24”x60” footprint and is fully lined in mylar on the inside.
So my questions are:
1) How close should I put the lights to my plants? Everyone online says 18” but why not closer?
2) Why does the sun not burn plants at 1500 PPFD, but my LED’s will?
3) Should I get a PAR meter so I can test better?
4) Is sunlight always better than indoor lights, or is it possible to do better grows indoors than outside?

Click to expand...

Aqua Man said:

Ok I have a ghetto app that's better than nothing. It will get you in the ball park bit always go by plant response.

"Light meter" by "my mobile tools dev" it's only for Android. Free download use with the screen facing up at the top of the plant.

Some increase light faster this is what works for me.

Clones/seedlings 5000-10000 lux
Veg 15k-45k start at 15k lux and increase 5000-7500 a week. Some do more.

Flower 45-65k 65-80k if CO2 of about 1000ppm. This is safe numbers not that you may not be able to push it a bit more.

Now also consider you need to pay attention to leaf temps when getting up in numbers. Just cause the plant can handle the light it does not mean it can handle the temps. The amount of IR produced by the light, room temp, humidity and airflow will play a major role in that.

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scyncegrown said:

That’s a solid app. Used it a few times around the office.
I imagine the succulents going under these lights could take a higher lux and heat? I’m curious to see if Co2 will be used for them!? It would be dope if so. I’m guessing they have limited uptake compared to what we are used too. The thicker leaf cover results in limited stomatal growth.
I’ve seen folks run succulents at way higher leaf temps. Guess it might be the built in sunscreen.

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Aqua Man said:

Yeah some run as high as 85f leaf temps with CO2. Without I believe 75f is the optimal leaf temps for photosynthesis and while higher will work it does have a negative impact on overall photosynthetic rates. Temps are important both root and leaf.

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