LED Grow light distance to seedlings

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zeuspaul
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LED Grow light distance to seedlings

#1

Post: # 38116Unread post zeuspaul
Mon Jan 11, 2021 5:15 pm

What is a good way to determine the proper distance? Is lux a good metric? I have seen recommendations ranging from 3 inches to 36 inches. I assume the variation is due to light intensity. This is my first year using grow lights. I usually carry my seedlings in and out every day. I am starting more seedlings because the local nurseries failed me last year.


One of the ones I am using is this 100 watt (actual 20 watt) which has a generic recommendation of 24 to 28 inches for seedlings and no lux rating.

This guy https://bioslighting.com/horticulture-l ... nce-chart/ recommends about 36 inches for seedlings and 3663 lux but uses a 600 watt bulb.

Wikipedia https://en.wikipedia.org/wiki/Lux indicates an overcast day is 1000 lux, full daylight (not direct sun) is 10,000 to 25,000 lux, and direct sun is 32,000 to 100,000 lux.


I also have this 150 watt (actual 30 watt) light with no seedling rec but does have lux ratings. Using a 4000 lux guess I would use 20 inches above the seedlings.

I want to use as much light as I can. 4000 lux seems like it might be too little as it is only between overcast and full daylight but not direct sun. Wouldn't more light reduce the need for hardening off? In the past I have placed the seedlings in direct sun from day one. What should I look for as the seedlings progress to determine if they are getting too much or too little light?
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TLC333
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Re: LED Grow light distance to seedlings

#2

Post: # 38216Unread post TLC333
Tue Jan 12, 2021 11:14 pm

This is a big debate! I've been growing indoors with various types of grow lights and shop lights with different watts, lumens, etc. There really isn't a clear answer. So I will give you my "rule of thumb".
Do your LED's produce any kind of heat? If so, are we talking warmth to decent heat or scorching hot?

Example: my first true red and blue grow lights were LEDS. They got surprisingly warm. I wouldn't say hot but what does that mean to a seedling? catch my drift? So with these lights, I kept at least 2 inches until they were growing so fast keeping them 6 inches above was necessary as long as they weren't reaching for the light. Why 2 inches? Because 2 inches is the happy place where my seedlings weren't reaching for more light but also they were not quickly wilting or drying out from too much heat or other unmentioned stresses.

If your light produces very little or no warmth of any kind......you have to base it on what the plant tells you.

Keeping lights with in 4 inches is ideal to avoid any stretching or reaching for light AKA Legginess. If your light isn't touching the tops of your seedlings I would say get as close as you can with in an inch from the top of your seedlings. My newest lights are crazy crazy bright and DO NOT produce any warmth. When the time comes I will comfortably keep them with in an inch or 2 of my seedlings. I did this with my strawberry seeds as well, still worked great since those seeds need the light to germinate.
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Cole_Robbie
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Re: LED Grow light distance to seedlings

#3

Post: # 38218Unread post Cole_Robbie
Wed Jan 13, 2021 12:01 am

Hardening off in regard to light mostly has to do with adjusting an indoor plant to sunlight gradually. It does not matter how intense the indoor light is, the plant will still require a gradual adjustment to the rays of the sun. Set them out in the shade for a few days.
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Rockoe10
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Re: LED Grow light distance to seedlings

#4

Post: # 38240Unread post Rockoe10
Wed Jan 13, 2021 1:07 pm

I get my LED as close as i can. My leaves even reach and touch them if i wait a couple extra days before moving it up.

If you keep the lights to far away, it wastes A LOT of energy. If the lights you have put off to much heat to get close, then I would recommended using a light with less intensity and heat, that way you can get closer. Otherwise, you are just wasting money on your electric bill.
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rossomendblot
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Re: LED Grow light distance to seedlings

#5

Post: # 38243Unread post rossomendblot
Wed Jan 13, 2021 3:10 pm

Is there a link or image missing in your post? I can't see which lights you are using.

With LEDs it's usually high light intensity that causes scorching, not heat. The more intense the light the further the away the plants need to be. My grow light uses some of the most efficient diodes currently available and I have grown 9 micro tomatoes from seed to harvest using 45W of power. It currently hangs around 12 inches above the canopy, which is the minimum recommendation from the manufacturer. Last time I measured it was about 20,000 lux at the canopy. For seedlings I would prefer 18 inches or more, but my tent isn't tall enough so I will just dim the light to 20W or so instead and increase the power as they get bigger.
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zeuspaul
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Re: LED Grow light distance to seedlings

#6

Post: # 38249Unread post zeuspaul
Wed Jan 13, 2021 5:14 pm

The links show up in my browser. If you enter the product number B0834K2B41 at Amazon it is the 100 watt (20 watt actual bulb. B08FHW22LM is the product number for the 150 watt (30 watt actual). Google will return the third link searching for bioslighting LED Grow Lights Distance for Cannabis & Other Plants

I don't know why it is not showing up for you.
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Last edited by zeuspaul on Wed Jan 13, 2021 8:59 pm, edited 1 time in total.

zeuspaul
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Re: LED Grow light distance to seedlings

#7

Post: # 38251Unread post zeuspaul
Wed Jan 13, 2021 5:23 pm

Do these links work? In my original links I deleted the tail end of the links because they had references which I thought were irrelevant.

100 watt

150 watt
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Growing Coastal
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Re: LED Grow light distance to seedlings

#8

Post: # 38303Unread post Growing Coastal
Thu Jan 14, 2021 9:39 am

I see nothing
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Cole_Robbie
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Re: LED Grow light distance to seedlings

#9

Post: # 38323Unread post Cole_Robbie
Thu Jan 14, 2021 12:52 pm

Growing Coastal wrote:
Thu Jan 14, 2021 9:39 am
I see nothing
Did the site log you out? That happens to me every once in a while.
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Harry Cabluck
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Re: LED Grow light distance to seedlings

#10

Post: # 38568Unread post Harry Cabluck
Sat Jan 16, 2021 10:18 pm

zeuspaul: The folks at Fluence Bioengineering in Austin, Texas have a website that is easy to tour. They make fine fixtures and their site has lots of information. https://fluence.science/
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Growing Coastal
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Re: LED Grow light distance to seedlings

#11

Post: # 38617Unread post Growing Coastal
Sun Jan 17, 2021 10:59 am

Cole_Robbie wrote:
Thu Jan 14, 2021 12:52 pm
Growing Coastal wrote:
Thu Jan 14, 2021 9:39 am
I see nothing
Did the site log you out? That happens to me every once in a while.
No.
Adblock?
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