Mammoth Lighting Spectrum Tuning Handbook

Please note - this is a working document and we will be making adjustments over time. Check back often and feel free to add comments or suggestions for the community. 

Executive Summary

At Mammoth Lighting, we believe that approximately 95% of growers should operate a high-quality, fixed, full-spectrum LED that closely mirrors natural sunlight — such as the Nova Sun Series.

Why?

Because spectrum tuning, when applied without a deep understanding of plant photobiology, often introduces unintended consequences:

• Reduced PPFD (fewer photons = less growth/yield)

• Spectral imbalance = pigment under-activation and less plant expression

• Increased plant stress

• Inconsistent morphology and quality

Put simply:

Many growers believe they are helping their plants by tuning spectrum, when in reality they may be doing more harm than good.

A properly engineered full-spectrum fixture already supports:

• Photosynthesis

• Photomorphogenesis

• Secondary metabolite pathways

• Canopy penetration

For most facilities, the best performance gains come from optimizing:

• PPFD

• Uniformity

• Temperature

• VPD

• CO₂

—not from adjusting color channels.

That said, for advanced growers, breeders, and R&D programs, spectrum tuning can be extremely valuable when used correctly. This handbook explains how to do that safely and effectively.

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The Mammoth Philosophy: Follow Nature First, Then Apply Science

Why Balanced Spectrum Matters

Plants evolved under a continuously shifting, broadband solar spectrum. They do not respond to single colors — they respond to ratios between wavelengths and total photon flux.

Many LED fixtures on the market still follow an outdated design philosophy:

• Heavy red for diode efficacy

• Minimal green and amber

• Limited far-red integration

This approach targets chlorophyll absorption but ignores:

• Accessory pigments

• Canopy light distribution

• Hormonal signaling

• Stress buffering mechanisms

Red diodes can exceed 4.0 µmol/J, which looks great on spec sheets, but:

High Red Spectrum = photoinhibition and poor plant expression

Excessively red-weighted spectra often result in:

• Increased stretch

• Weaker stems

• Less uniform canopy development

• Reduced terpene and secondary metabolite expression

Mammoth designs around plant response, not diode marketing metrics.

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Why Full-Spectrum Matters: Pigments and Light Harvesting

Relative Pigment Absorption Across the Spectrum (with Functional Context)

Below is a relative absorption overlay of major plant pigments across the PAR and far‑red regions. Curves are normalized to 1.0 relative absorption to show where pigments are active, not just whether they exist. This matters because plant responses are driven by overlapping pigment systems, not isolated peaks.

 

How to read this graph:

• Each curve represents the relative absorption efficiency of a pigment family.

• Arrows indicate the wavelength regions where each pigment contributes most strongly to energy capture or signaling.

• Overlap zones are where energy transfer between pigments is most efficient.

This is why simply targeting chlorophyll peaks (blue/red) ignores:

• canopy penetration (green–amber)

• stress buffering (carotenoids)

• phytochrome signaling (far‑red)

A spectrum that is "tunable" but missing entire regions cannot be fixed by "tuning"— the photons are simply not there.

"Photosynthesis in crop canopies is driven by the integrated action of multiple pigments and wavelength regions, not only chlorophyll absorption maxima." — Smith et al., 2017

Major Pigments and What They Support

Pigment	Peak Activity (Approx)	Primary Role in Plant Function
Chlorophyll a	~430 nm, ~660 nm	Core photosynthetic reaction centers
Chlorophyll b	~450 nm, ~640 nm	Expands usable spectrum, improves quantum efficiency
Carotenoids (β‑carotene, xanthophylls)	~470–520 nm	Photoprotection, thermal dissipation, stress buffering
Phycoerythrin (algal analogue)	~540–570 nm	Demonstrates importance of green/yellow capture & transfer
Phycocyanin / Allophycocyanin	~600–650 nm	Energy funneling toward PSII (model systems)
Phytochrome (Pr / Pfr)	~660 / ~730 nm	Flowering signals, morphology, shade responses

"Green photons contribute significantly to whole‑canopy photosynthesis due to deeper penetration and redistribution within leaves." — Terashima et al., 2009

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Critical Warning: Unintended Consequences of Spectrum Tuning

Before tuning, growers must understand the trade-offs.

1. Reducing Channels Reduces PPFD

Yield is strongly correlated with total photons.  In many studies 1:1 (1% increase in light = 1% increase in yield)

When PPFD is held constant, spectral effects on yield are often smaller than the effect of QUALITY alone.

If tuning reduces PPFD by 10%, growers should expect potential yield loss.

2. Spectral Narrowing Increases Stress

Extreme blue:

• Suppresses leaf expansion

• Reduces canopy closure

Extreme red:

• Increases elongation

• Weakens structural integrity

Narrow spectra may manipulate morphology, but they rarely outperform balanced white spectra in production environments.

3. Tuning Cannot Fix Poor Spectrum

Adding tunable channels to an already unbalanced fixture does not recreate full solar biology.

A poor spectrum, even when tuned, remains biologically limited.

This is why Mammoth always starts with full spectral coverage and then applies tuning as a fine adjustment.

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SECTION 1 — MAMMOTH'S #1 RECOMMENDATION: SEASONAL & DIURNAL SHIFTS (FOLLOWING NATURE)

These settings reflect:

• Atmospheric scattering

• Solar elevation

• Plant photoreceptor behavior

Key principles:

• Dawn and dusk are warmer with relatively higher far-red

• Midday is highest Kelvin and bluest

• Summer has the strongest blue and highest irradiance

Far-red is never eliminated, but slightly elevated at low solar angles.

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Master Seasonal Spectrum Targets (Midday)

Season	Target CCT	Blue %	Green %	Red %	Far-Red %	Biological Goal
Spring	5400–5600 K	24	32	36	8	Vegetative expansion with structure
Summer	5800–6200 K	28	30	33	7	Maximum metabolism & canopy density
Fall	4000–4200 K	17	32	41	10	Flower bulking and maturation

 

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Diurnal Profiles

🌱 Spring

Phase	Duration	CCT	Blue %	Green %	Red %	Far-Red %
Dawn	1h	4200 K	18	34	38	10
Morning	4h	5200 K	22	32	38	8
Midday	4h	5600 K	24	32	36	8
Afternoon	4h	5200 K	22	32	38	8
Dusk	1h	3800 K	16	36	36	12

☀️ Summer

Phase	Duration	CCT	Blue %	Green %	Red %	Far-Red %
Dawn	1h	4600 K	20	32	36	12
Morning	5h	5600 K	26	30	36	8
Midday	4h	6200 K	28	30	34	8
Afternoon	5h	5600 K	26	30	36	8
Dusk	1h	4000 K	18	34	36	12

🍂 Fall

Phase	Duration	CCT	Blue %	Green %	Red %	Far-Red %
Dawn	1h	3800 K	16	36	36	12
Morning	3h	4200 K	18	34	36	12
Midday	4h	4200 K	18	34	40	8
Afternoon	3h	4000 K	17	34	41	8
Dusk	1h	3400 K	14	38	36	12

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SECTION 2 — ADVANCED GROWER R&D PLAYBOOK

These strategies are optional tools for experienced cultivators who already have:

• excellent environmental control

• dialed‑in nutrition

• strong cultivar knowledge

They are intended to fine‑tune morphology or expression — not to compensate for weak spectrum design.

Core Rule of Mammoth R&D Philosophy

Never sacrifice total photons or spectral completeness in order to chase a single plant response.

Whenever spectral channels are adjusted, total PPFD should remain constant and no major waveband should be eliminated.

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Recommended Spectrum Tuning Strategies

Below are evidence-based lighting strategies designed for advanced growers and R&D teams to optimize plant morphology, secondary metabolite expression, integrated pest management, and energy efficiency — without sacrificing total photon delivery.

Strategy #1 — Follow Nature (Seasonal & Diurnal Light Cues)

Follow the above grids for Spring / Summer / Fall using a Controller and Spectrometer. 

Plants integrate light cues through multiple photoreceptors (cryptochromes, phototropins, phytochromes) to regulate:

• flowering cues

• leaf orientation and expansion

• shade responses and internode elongation

Key Principle

Trigger photoreceptor signaling pathways without reducing carbon-driving photons.

This means:

• gently shifting spectral ratios instead of aggressively dimming or eliminating wavelengths

• applying changes over limited windows (hours/days, not weeks)

Recommended Approach

• implement small ratio changes for specific physiological cues

• avoid “spectral starvation” (reducing photons to elicit a signal)

• use a PAR Meter with spectrometer capability and a programmable controller

Use Case: fine-tuning flowering onset, leaf angle adjustment, and minimizing stress responses.

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Strategy #2 — Late-Flower Blue & UV for Secondary Metabolite Expression

Research across cannabis and high-light crops shows that short-term exposure to additional high-energy wavelengths (blue + UV) can stimulate chemical defense and secondary metabolite pathways late in flowering.

Quote

“Supplemental UV-B increased cannabinoid concentration but reduced inflorescence mass when applied throughout flowering. Short-duration treatments may improve quality with less yield penalty.” — Magagnini et al., 2018

Takeaways

• chemical expression can increase with UV exposure but continuous exposure can reduce biomass

• timing and duration matter

Mammoth Recommendation

• apply modest blue + UV increases in the final 2–3 weeks of flower

• increase blue gradually into flower to avoid early-stage stress

Use Case: boutique genetics, terpene-focused cultivars, phenotype selection.

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Strategy #3 — Far-Red for Morphology, Flowering Signals & Efficiency

Far-red (FR) photons influence phytochrome equilibrium (Pr ⇄ Pfr), affecting internode length, leaf expansion, and flowering signaling.

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What Recent Cannabis Research Shows

A 2025 Scientific Reports paper investigated whether far-red could replace hours of full spectrum light with a shortened photoperiod and still maintain or improve yield and cannabinoid expression.

Key Findings

“The THC concentrations were elevated in both high THC varieties by the different far-red treatments.” — Nature Scientific Reports, 2025. Nature

Specifically:

• In Northern Lights, a schedule of 10 hours full light + 2 hours FR in darkness (“10L_2D”) produced nearly 70% higher total cannabinoid yields than a traditional 12-hour photoperiod. Nature

• This schedule also resulted in ~5.5% energy savings and lower carbon emissions compared to standard 12-hour lighting. Nature

“A lighting schedule of 10L_2D instead of 12L would result in a saving of 5.5% in power usage and resultant emissions.” — Nature Scientific Reports, 2025. Nature

These results show that timed FR applications can simultaneously improve cannabinoid production and lower energy consumption when paired with balanced baseline light.

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Broader Photobiology Support

“Far-red photons are as efficient as traditionally defined photosynthetic photons when included in total PPF.” — Zhen & Bugbee, 2020

This confirms FR should be considered part of useful light, not ignored. Nature

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Far-Red Implementation Options

• Option 1 — Continuous Low-Level Far-Red
  ~3–8% of total spectrum, good for controlled shade avoidance responses and leaf expansion.

• Option 2 — End-of-Day (EOD) Far-Red in Darkness (Experimental)
  15–120 minutes at lights-off can mimic natural dusk FR, supporting phytochrome transitions. Recent research supports energy and quality gains with this approach. Nature.

Mammoth Position:
Continuous FR during photoperiod yields more reproducible morphology effects; EOD FR is best treated as experimental R&D.  We have NOT seen evidence EOD FR puts plants to sleep any faster than full time FR.  Same with Dr. Bugbee using controlled growth chambers.  We encourage experimentation - but cannot recommend (faster flower) until there is scientific evidence.  

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Strategy #4 — Strain-Specific Spectral Profiles (Equatorial / Sativa-Dominant)

Many sativa-dominant and equatorial genetics evolved under higher midday blue exposure.

Photomorphogenic Support

“Blue light increases leaf thickness, chloroplast density, and photosynthetic capacity per unit leaf area.” — Hogewoning et al., 2010. Nature

Key Principles

• higher blue fraction encourages compact internode spacing

• improves mechanical strength and canopy uniformity

• counters stretch seen in red-dominant spectra

Mammoth Recommendation

• increase blue fraction by ~5–10% relative to baseline

• maintain green and red support

• keep FR moderate

Use Case: breeding, phenotype selection, mother stock conditioning.

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Strategy #5 — UV for Integrated Pest & Pathogen Management (IPM)

Ultraviolet light has been shown to directly suppress pathogens like powdery and downy mildews when applied at night, exploiting the fact that pathogens can repair UV damage with blue light, which is absent in darkness.

Cornell Research

• Cornell AgriTech researchers found that nighttime UV treatments can control powdery mildew and other pathogens because pathogens’ blue-dependent DNA repair is inactive at night. Cornell CALS

“What makes it possible for us to use UV to control these plant pathogens is we apply it at night...the pathogens don’t receive blue light and the repair mechanism isn’t working.” — Cornell AgriTech research team. Cornell CALS

Peer-Reviewed Support

• Nighttime ultraviolet (UV-C) irradiation has been shown to reduce powdery mildew sporulation and germination without harming plants in controlled trials. PubMed

• Direct night UV applications in agricultural settings can suppress pathogenic fungi with efficacy comparable to traditional fungicides. Cornell CALS

Mammoth IPM Recommendation

• apply UV at 30 min after lights-off and 30 min before lights-on

• low dose and short exposure maximize pathogen suppression while minimizing plant stress

• integrate with environmental and cultural controls

Use Case: IPM against powdery mildew, downy mildew, and surface pathogens in protected environments.

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Strategy #6 — Increase Blue Spectrum for Veg, Clones, Moms & Vertical Systems

Higher proportions of blue light influence cryptochrome and phototropin pathways that control compact morphology and leaf development.

Research Evidence

• Blue light enhances leaf thickness and chloroplast density, improving photosynthetic capacity per unit leaf area. Iowa State University Extension

• Excessive blue can reduce total biomass if applied without context, so balance is key. PubMed

Recommendations

• increase blue fraction during vegetative, cloning, and mother plant phases (~5–15% above baseline)

• monitor compactness and adjust if growth becomes overly suppressed

• in vertical production systems, higher blue helps maintain tighter internode spacing and better use of vertical space

Use Case: vertical farms, mother rooms, clone beds, and compact veg cycles.

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Final R&D Guidance & Grower Guardrails

Always ensure:

• Full spectral coverage (do not eliminate critical wavelengths)

• Constant total photon delivery (PPFD) — tuning should shift ratios, not reduce photons

• Cultivar-specific tracking (data logging and phenotype response)

If spectrum tuning reduces PPFD or removes spectral bands, it is not optimization — it is nutrient deprivation in photon form.

Mammoth encourages experimentation within these guardrails so tuning remains an effective performance tool, not a production risk.

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Final Takeaway — Mammoth Philosophy

Spectrum tuning is powerful only when built on a complete, balanced spectrum.
Mammoth Lighting systems are engineered to:

• activate all pigment and photoreceptor systems

• maintain PPFD while tuning

• shift balance without eliminating wavelengths

This allows growers to:

• follow nature for reliable production

• apply advanced R&D strategies safely and effectively

Guided by Nature. Confirmed by Science.

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Expanded Academic References (with sources)

• Peterswald, T.J. et al. (2025). The effects of far-red light on medicinal Cannabis. Scientific Reports. “THC concentrations were elevated…added 2 h of far-red in darkness increased total cannabinoid yields…result in a 5.5% saving on power usage and emissions.” Nature

• Zhen, S. & Bugbee, B. (2020). Far-red photons have equivalent efficiency when included in total PPF. Nature

• Magagnini, G. et al. (2018). Supplemental UV-B increases cannabinoids but can reduce biomass. Nature

• Cornell AgriTech research on nighttime UV light controlling pathogens. Cornell CALS

• Nighttime UV-C suppresses powdery mildew in controlled environments. PubMed

• Midwest Grape & Wine Institute on nighttime UV pathogen control mechanisms. Iowa State University Extension