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Is Spectrum Tuning/Adjustment a Scam for LED Grow Lights?

December 12 2022 – Danielle Daly

Led Grow Light Spectrum Tuning
Led Grow Light Spectrum Tuning

Is Spectrum Tuning a Scam?  The better question is:  Are the benefits of spectrum tuning overexaggerated and some of the proposed formulas counterproductive…. We think so – thoughts below:

It’s the #1 question we get, and we will give you some initial thoughts and answers below and why we do not build a light with Spectrum adjustment.  It really comes down to the Science and a Cost/Benefit analysis. 

Today’s focus will be End of Day (EOD) Far Red. However, we will follow up on some of the popular formulas (below) in a future post….

For example:  A common proposal is to deliver more red (vs blue) during flower.  Yes, we do have empirical evidence that this does increase yields.  Other studies show additional blue in the spectrum increase cannabinoids (THC, CBD).  So you need to ask the below questions: 

  1. By increasing the Red.. to increase yields…did you Reduce cannabinoids as the Science would suggest?
  2. When you increased the red and decreased the blue…did you lower overall light intensity/ppfd and Yield (light intensity and yield are linear with an R2 of .88)?
  3. If your light has power adjustment to deliver the same canopy ppfd during the adjustment phase – what is the max amperage per diode? If they are running too high/hot…you are reducing the overall life of that diode?
  4. Would it better to just have a light with more blue and more red full time…with heavy light intensity as the Science would suggest? Such as the Mammoth Mint White Series 😊

End of Day (EOD) Far Red.

Looks pretty cool right?  All that Red Light to put the plants to “sleep” faster.  Zero research to support this.  There is evidence to include Far Red full time in your spectrum as all Mammoth Lights incorporate. 

Effects of Continuous or End-of-Day Far-Red Light on Tomato Plant Growth, Morphology, Light Absorption, and Fruit Production: Kalaitzoglou 2019

“Leaf area and plant dry mass were lower in the treatments completely lacking FR than treatments with FR. EOD-FR-treated plants responded almost similarly to plants grown without FR, except for plant height, which was increased.

Additionally, the treatments without FR and the EOD-FR showed strongly reduced fruit production due to reduced fruit growth associated with reduced source strength and delayed flowering.

Photons from NIR LEDs can delay flowering in short-day soybean and Cannabis: Implications for phytochrome activity. Kusuma P, Westmoreland FM, Zhen S, Bugbee B (2021)

“Photons during the dark period delay flowering in short-day plants (SDP). Red photons applied at night convert phytochromes to the active far-red absorbing form (Pfr), leading to inhibition of flowering.”

Our Conclusion: The only effect of EOD Far Red is to increase stem elongation (as concluded by the study on SDL poinsettia's) as the plant is tricked into the shade avoidance and no effect on flowering time.  


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