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Old June 15, 2019   #1
Billm302
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Default Best color light for seedlings

I recently moved and no longer have a “sunroom” where I can start my seedlings. I want to use fluorescent fixtures for my next seedlings. What color light is best for seedlings. I seem to remember that the recommendation used to be to mix cool white with warm white bulbs but wonder if 6500k bulbs might be better. Any thoughts would be appreciated.
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Old June 16, 2019   #2
Nematode
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I can't comment on fluorescent color temp, but if you have a big budget, I have found LEDs vastly superior to fluorescents. LEDs can achieve sunlight levels in your starter box.
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Old June 16, 2019   #3
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6500k is the best all around light to use.
It mimics the sun at noon and has all the red and blue light you need.
Don't get wrapped up in the color spectrum for budding and so on.
Much of this comes from pot growers wanting their plants to bud which is yet another sales pitch to buy more stuff.

It is daylight hours that cause budding not light spectrum in pot.
In reality it is longer hours of uninterrupted darkness.
It just so happens that that spectrum changes somewhat in the fall of the year.
Tomatoes are not sensitive to daylight hours and budding.
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Old June 16, 2019   #4
xellos99
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6400k works well
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Old June 16, 2019   #5
slugworth
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I use a mix of 5000K and 6500K bulbs about 18 inches above the trays.
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Old June 16, 2019   #6
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Many of these lights have uses on them and it is hard to find the spectrum at time.
The 65000K will say for active places.
The lights more on the red side will say something else and are more soothing to the eyes.
Lumens have nothing to do with color of the light and are measured in the green or middle spectrum picked up by humans not so much with plants.
This is why you see true LED grow lights that look purple.
They are red and blue spectrum hence the purple or violet color.
They are very bright but not white bright.
Since plants are green they will reflect most f not all of the green light right back off of the leaves.
From what I have read.
Correct me if I am wrong.
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Old June 16, 2019   #7
Nematode
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UV leds activating white phosphor is very efficient.
Even though the green in the spectrum is not used by the plants, overall electron to photosynthetic efficacy is very high for these white LEDs. ( yup I'm a dorky EE)
It's also easy to diagnose them under white light as opposed to the blue red lights where your eye can't make sense of what the plants look like.
Sorry OP, a bit off topic.
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Old June 16, 2019   #8
slugworth
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To over-winter plants that I don't want to get huge I use 5000K plus lower room temps keeps them
alive but not getting too big.
A blank cd (if you still have such a thing) held at an angle to the light acts like a poor man's prism.
Comes in handy for lights that aren't marked with the K rating.
https://lightandcolorlab.wordpress.c...-prism-effect/
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Old June 16, 2019   #9
Worth1
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You can still order prisms too.
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Old June 16, 2019   #10
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Whats a CD?

Jk
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Old June 17, 2019   #11
SharonRossy
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I use the T5 HO lights but will convert to LED slowly. The white lights. They apparently don’t get hot and have a great penetration through the leaf canopy and are very efficient. They are,however, expensive.
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