Why LED is the Light of Choice for Indoor Plants

Growing LED
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LEDs are rapidly becoming the light source of choice for indoor horticulture connoisseurs. This is due to the ability of the light spectra of LEDs to be tailored to meet the nutritional needs of the plant – something traditional legacy horticulture lights cannot do.

Tessa Pocock PhD, a senior research scientist at the Centre for Lighting Enabled Systems and Applications (LESA) at Rensselaer Polytechnic Institute in NY, conducted a study to better understand the effect of customizable light sources and how this impacts plant growth. The study showed that the ability to customise the light spectra using LED lighting leads to many positive benefits. Benefits proven include greater energy efficiency, higher yield and improved concentrations of essential nutrients which contribute to human health.

In the study a red lettuce cultivar (Rouxai) was grown under different light treatments and compared against several key indicators: Yield (as determined by fresh weight), anthocyanin, carotenoid and chlorophyll concentrations and photochemistry. Yields were shown to be significantly higher in seedlings grown under Lime + Purple and Purple + Green LEDs compared to other light sources. Both LED combinations contain far red output (700 – 800 nm), and it is well accepted that far red increases cell elongation and leaf size. Additionally, higher anthocyanin and chlorophyll concentrations were also observed in these light combinations than other conventional light sources.

Conventional light sources operate on a “Photosynthetically Active Radiation” (PAR) spectra of 400nm to 700nm, meaning conventional lamps cannot target the far red (700 – 800nm) wavelengths that maximise yield in the same way customizable LEDs can.

Studies such as this demonstrate the significant advantages for the use of LEDs over traditional light sources for crops in indoor environments.

For more detail, read Tessa Pocock’s full white paper titled ‘Luxeon SunPus Series Lime LEDs Produce High Yield and Nutrition in Leafy Greens’ (https://www.lumileds.com/uploads/702/WP34-pdf) to learn more.

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Hey Ben,

Thank you for this. I was curious about your IR output. Historically, LEDs have almost zero heat signature, but most don’t spike into the IR spectrum (750nm+), we usually see a focus on the Visible spectrum, with an emphasis on the High Energy Visible (400nm-500nm), or probably better known as blue light. Granted, at 800nm, you are just dipping your toe into IR, but I was curious if that far red production was increasing your heat signature? Thanks!

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Typically the Far Red spectrum used in horticultural LED is within 700-740 nm. That’s why we do not call it IR. Plants do not like the heat from IR either.

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Exactly…normally IR is a bad thing, but this LED is said to hit 800nm, so that is why I was curious about heat signatures.

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What if you’re able to control it?

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Hey @bmiller…is your question directed at me, @yrenbutcher or @ben_spectrah? I have ZERO data from their end, but my gut assumption is that output over the 750+nm spectrum would have to have some level of IR, even with LEDs, but I doubt that it would be significant…but that is why I asked the question as well. Are you able to hit the far red (passed 750nm) without affecting the heat signature?

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We’ve come across several University studies that conclude IR enhances transpiration. Yes our LEDs are able to hit far red. Our purpose for doing this is to indeed affect the leaf temperature resulting in better transpiration :wink:

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Awesome…that is exactly what I was thinking! Thank you for the reply.

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How is the efficacy of the LumiLEDs? Which blend are you using for your product? Can you drop links to IR based papers? @ben_spectrah

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Hey @BG_SAGE, we are using the LumiLEDS 12.5% blue Sunplus COB which has phenomenal results! In regards to IR, using this COB, we only emit a very small percentage of far red. The red to far red ratio is about 5.3 - please see the white paper i linked above for more details.

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