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Old 05-05-2024, 12:22 PM
knewt knewt is offline
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Default Which Spectrum ?

I'm trying to think ahead to next winter, when I bring my orchids in.
In NW Florida, the nights can drop below 60º from sometime in Oct, until Apr (it varies), so the plants are inside during the cooler months.

Anyway, I'm thinking of some LED lights for the shelf unit I'm planning to use - It's in a south-facing window, so it will get daylight during part of the day, but, because of trees and the angle of the house, not all day.
And, if last year was any indication, we can get a solid week or so at a time of overcast and rain, sometimes.

So, I'd like to get some supplemental lights.
If you had to choose between 2 lights, with these 2 spectral graphs, which would you choose for general lighting for a selection of various orchid genera - Of course I will modify placement for their different intensity requirements, but which one would work better, in general.
Both are sold as "Full Spectrum", but obviously are different color temperatures - One is 5000K, the other about 3000K.

I know there are much better lights, but am NOT looking for specific brand recommendations, as there are severe budget constraints - One or the other of these will have to do.

Light #1


Thanks for any advice.
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Old 05-05-2024, 01:01 PM
estación seca's Avatar
estación seca estación seca is offline
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Given your location, your plants won't be as dependent on supplemental lighting as will those of people farther north. The difference in spectrum probably won't be significant for your plants.

But - do the vendors provide information about total light output? If both are in your budget I would pick the one with higher light output. It might be reported in foot candles, lumens, lux, PAR (photosynthetically active radiation) or other units.

Edit: Color temperature (reported in degrees Kelvin) is a measurement of how the light looks to a human eye. It has no effect at all on how plants grow. Different lamps might have the same color temperature but grow plants poorly, adequately or very well. What matters is how many photons are emitted that the plants can use. That is measured by PAR, and the spectrum emitted affects the PAR measurement.

By an accident of chemistry old technology fluorescent tubes with a color temperature of 5,000-6,000 K were excellent for growing plants, and marketers now try to tell people color temperature is important. It isn't.
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Last edited by estación seca; 05-05-2024 at 01:06 PM..
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Old 05-05-2024, 02:41 PM
knewt knewt is offline
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That's the thing, I guess - The mfg says the lumen output is the same for both colors @ 24W per light.
They'll be in a living space which we'll use part of the time they're on, and we'll have to live with the light color, so that's a factor. But I want what's best for the plants.

As far as appearance goes, I've used 5000-6500K led's for aquariums, but the effect is different going through water - Not as "Bright White" that way.
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Old 05-05-2024, 06:35 PM
pure bliss pure bliss is offline

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hi knewt.
Orchids are able to absorb the energy from blue and red light most. The other colors are equally important to provide but in much lower amount.

A white light provides all spectrums of light with either more blue or more red light.

5000k is more blue light
3000k is more red light.

Generally one says the blue is better for vegetative growth and red is better for flowering but this is technically not true. Plants will grow just fine under either blue or red but the main reason in my opinion why red is recommended for flowering is because flowering requires most energy and the red spectrum is the one that plants can absorb the most efficiently, they get more energy per watt from red than blue.

Now you can't just use red, that would result in terrible growth. But a bit more red will provide the plant with more energy than blue.

So personally I prefer 3000k which has more red and is thus a more orange light (warm white compared to cool white).

It should provide more energy per watt than more blue and thus the plants will grow better.

Some would say blue results in more compact growth and red in more taller growth but I have not found this to be true.

You can influence growth with the fertilizer you use far more.

A fertilizer high in nitrogen will result in tall growth. Good for outdoor growers. A fertilizer high in potassium will result in compact growth, ideal for indoor growers.

So yeah go with the 3000k if you ask me. It will provide the most useable energy for the plant.
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Old 05-06-2024, 07:42 AM
knewt knewt is offline
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Thanks for the well reasoned reply.
I think I'm going with the 3000K lights, first, it will be in a living space, and I think they'd be easier on the eyes.
But also, if the red end of the spectrum promotes flowering, even slightly, it's what orchids are all about, at least to me
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Old 05-06-2024, 08:17 AM
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Ray Ray is offline
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I will add that anyone looking into LED plant light should check out botanicalleds.com.

The owner is an orchid grower, and he used both a par meter and spectrophotometer to design the lamps, and as far as I can tell, they are the best “bang for the buck” out there.
Ray Barkalow, Orchid Iconoclast
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Old Yesterday, 11:13 AM
Kittyfrex Kittyfrex is offline
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While i would suggest growth lights always, supplementing low-light species can be done with 'simple' LED bulbs. I have 5 above where my orchids overwinter (and phals stay all year long).
It has been going on for 3 and half years, and started of as an experiment. Results? Phals and oncidiums do quite well, growing and blooming without hinge. I would advise against trying anything that likes more light; it may grow, but it will likely not bloom if it's kept under such lights year round.

Before anyone blasts me for saying that, i am not using any old bulb i find, i am specific about color/strenght. They are also quite high from the plants, so it's possible lowering them could do better on other species, but those only need to be under lights in winter.
It was an experiment at the beggining, but the results have been so good, i have no intention of moving my phals/oncids any time soon.
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