Technical Guide: Implementing Under Canopy Lighting Systems

Prepared by: Brian Gandy, Sustainable Terrains

February 4, 2026

1. Core Mechanism

Under canopy (UC) lighting represents a fundamental shift in controlled environment agriculture (CEA). The objective is to correct the spatial light disparity inherent in top-down lighting systems, in which lower canopy regions typically receive suboptimal Photosynthetic Photon Flux Density (PPFD).

• Mechanism: By directing light upward from the substrate level, we bypass the shading effect of the upper canopy leaves. This illuminates the underside of the canopy foliage, triggering stomatal opening and photosynthesis in previously underserved areas.

• Morphological Response: Leaves in the lower canopy will adapt to this new light source; within days, lower leaves may reorient or "flip" to capture upward-projected photons.
  

2. Economic Viability & ROI

Data indicates that UC lighting is transitioning from a trend to a competitive necessity, with the primary ROI driver being the conversion of low-value biomass ("larf") into premium flower.

• Yield Metrics: Studies show yield increases of 20% to 41%, depending on the integration strategy.

• Quality Shift: The most significant financial gain is the improvement in Average Quality Weighted Yield. UC lighting has been shown to increase bottom canopy flower density from <0.04 g/cm³ (larf) to >0.075 g/cm³ (A-Grade),.

• Compound Efficiency: Despite adding electrical load (approx. 30% increase), the grams per kilowatt-hour (g/kWh) efficiency improves because the additional biomass produced is of high market value rather than waste.
  

3. Fixture Specifications & Selection

Based on current benchmarking and direct sourcing analysis, the following technical specifications are recommended for commercial deployment.

Feature	Recommendation	Technical Justification
Wattage	120W – 160W	Sufficient intensity to penetrate the dense lower canopy without excessive thermal load.
Spectrum	60+% Red / Balanced	While high-red (80%) aids penetration, a balanced spectrum (60% Red) reduces the risk of photobleaching ("hash tipping") and improves visual diagnostics for plant health.
IP Rating	IP66 (Required)	Fixtures are located in the "splash zone" and must be resistant to dust, debris, and high-pressure water jets during sanitation.
Efficacy	≥ 3.0 µmol/J	High efficiency is critical to maintain the g/kWh ROI. Look for Design Lights Consortium (DLC) listed products.

4. Installation & Infrastructure

Deploying infrastructure at grower-height introduces workflow complexity. Correct installation is vital for safety and performance.

• Placement Height: Fixtures should be mounted 8–12 inches below the canopy leaves.

• Mounting Hardware: Utilization of tripod stands or adjustable legs is standard. Fixtures should not be placed directly on the media to allow airflow and allow for height adjustment as plants mature.

• Orientation: Ensure the linear optics and lenses face upward to target the underside of the canopy.

  
  

5. Operational SOPs: Timing & Plant Work

Implementing UC lighting requires a departure from standard cultivation Standard Operating Procedures (SOPs).

A. Lighting Schedule

• Vegetative/Transition: OFF. Do not use during veg or the first week of flower. Plants need time to root in the substrate after flipping without light stress.

• Activation: Turn on between Day 14 and Day 21 of Flower. This coincides with the end of the "stretch" and the beginning of bud site development.

• Intensity Ramping:

  • Start: 45–50% intensity to acclimate lower leaves.

  • Ramp: Increase to 100% by Day 18–21.

  • Late Flower: Consider dimming by 20% or turning off in Week 9 to prevent light stress during senescence.

    
    

B. Pruning & Defoliation

• Stop Heavy Lollipopping: Traditional heavy stripping of the bottom 1/3 is counterproductive. You must leave the lateral branches and bud sites you intend to illuminate.

• Selective De-leafing: Perform a "base cleanup" (bottom 6 inches) but focus defoliation on removing large fan leaves that block upward light penetration. A "light" de-leafing is often superior to a heavy strip.

  
  

6. Environmental & Fertigation Adjustments

Adding photon energy accelerates plant metabolism, requiring compensatory environmental changes.

• Transpiration & Humidity: UC lighting increases transpiration rates. Expect a humidity load increase and ensure HVAC/Dehumidification capacity can handle an additional 10–15% load.

• Fertigation (EC):

  • Plants will take up water and nutrients more quickly.

  • Expect to increase Input EC by 10% or maintain higher feed levels (e.g., 3.0–3.3 EC) for longer durations in the cycle.

  • Monitor runoff carefully; faster dry-backs may require increasing irrigation volume or frequency (P2 shots).

    
    

7. Industry Thought Leaders & Contributors

The data and protocols in this guide are synthesized from the following industry leaders and research trials:

• Faven Lighting: For extensive R&D on spectrum effects, far-red applications, and facility integration.

• Dr. Craig Hartsough & Texas Tech University: For rigorous scientific data on PPFD mapping, flower density analysis, and yield quantification.

• Nate (Cannacribs) & Growers House: For market analysis, DLC verification protocols, and comparative product reviews.

• Green Jeans Garden: For practical application of monocrop consistency and late-stage lighting integration.

• Thrive Agritech: For research on "A-Grade" vs. "B-Grade" bud conversion and chemical profiling.

• Gavita: For dimming protocols and acclimation schedules.

  
  

Bibliography of Sources

1. 2025 R&D Grow Room Results: The Truth About Far Red & Under Canopy Lighting (Transcript)

2. A scientific investigation of under canopy lights in cannabis production (Dr. Craig Hartsough, Texas Tech University)

3. BG 160W Under canopy Lighting Review (Brian Gandy, Sustainable Terrains)

4. BudBoost Installation Manual (P.L. Light Systems)

5. BudBoost Specification Sheet (P.L. Light Systems)

6. From Setup to Success: Implementing Gavita Under Canopy Fixtures (Gavita Transcript)

7. Growers House Under Canopy Lighting: Boost Yield, Quality & ROI (Cannacribs Transcript)

8. Growing with Faven (Faven Lighting User Guide)

9. Gavita Under Canopy 150W LED Manual (Hawthorne Gardening Company)

10. How We Are Using Undercanopy Lighting In Our Grow Rooms (Transcript)

11. ILUMINAR Lighting LED Under Canopy Spec Sheet (Iluminar)

12. Something I Said I Would Never Do... Under Canopy Lighting (Green Jeans Garden Transcript)

13. Sustainable Terrains LLC Mail - Under Canopy Pricing Update (Brian Gandy Email Correspondence)

14. Flexstar Under Canopy 120W Spec Sheet (Flexstar)

15. Thrive Agritech Under Canopy Lighting Report (Thrive Agritech White Paper)