The world of controlled environment agriculture (CEA) is transforming. For years, high-pressure sodium (HPS) fixtures dominated supplementary lighting in greenhouses. They were reliable, well-understood, and relatively straightforward in their operation. But in the last decade, light-emitting diode (LED) technology has matured to the point where its adoption is no longer a niche experiment—it is becoming the new industry standard.

Transitioning from HPS to LED lighting for horticulture is not just about lowering the electricity bill; it's also about enhancing the overall quality of the plants. It represents a more profound shift in how light, heat, and crop physiology are managed together. With LEDs, growers can separate heat from light, adjust intensity dynamically, and fine-tune spectrum ratios. This level of control offers efficiency gains and new opportunities but also demands new knowledge from growers and consultants alike.

Yet, the narrative isn’t one of immediate replacement. Many operations still rely on HPS for cost reasons, lifecycle planning, or simply because of familiarity. As policies restricting mercury-based lamps approach, especially in states like Washington with a 2029 deadline, growers are facing decisions about when—and how—to transition. Bridging today’s lamp-based systems with tomorrow’s LED infrastructure requires thoughtful, sustainable, and practical strategies.

More than anything, CEA lighting advancements are setting the stage for the next decade of optimization, automation, and integration. The decision facing growers is no longer whether to adopt LEDs but how to do so intelligently and sustainably.

In this edition of Horti-Gen Insights, we speak with Brian Gandy, horticulturist and founder of Sustainable Terrains, who has spent nearly a decade in horticultural lighting research, product development, and grower support. His insights combine agronomic expertise with practical strategies for transition and future-proofing CEA operations.

From Algae to LEDs: A Career Built on Light

Brian’s path into horticultural lighting started at the University of Georgia, where his early work focused on algae biomass production and wastewater remediation. There, he first saw how manipulating light spectra could influence biological growth. That foundation in applied photobiology would later guide his work as LEDs emerged as a viable option for production horticulture.

After years of managing organic farm operations in Georgia and Colorado, including season extension systems at high altitudes, Brian turned fully toward lighting in 2016. Since then, his focus has been on developing and applying sustainable lighting solutions for controlled environments, from product design to real-world implementation by growers.

HPS vs LED: Shifting from Automatic to Precision Control

The move from HPS fixtures to LEDs, Gandy explains, is like shifting from an automatic to a manual transmission:

• HPS delivers both heat and light simultaneously, with little control beyond fixture density.
  

• LEDs separate the two inputs, giving growers flexibility but also more responsibility to fine-tune their systems.

Two advantages stand out in the LED revolution for greenhouses:

• Optimization: LED systems offer dimmability, spectral control, and the ability to fine-tune daily light integral (DLI) strategies, allowing for precise control over lighting. This creates new opportunities for efficiency and crop-specific responses.
  

• Durability: Fixture lifespans are significantly longer, with gradual performance improvements continuing even as costs stabilize.

“LEDs give operators agility,” Gandy notes, “but you need to know how to drive them.”

Relamp & Relax: Bridging Today and Tomorrow

Not all growers are ready to switch overnight, and many are strategically extending the use of HPS while preparing for the future of LEDs. To address this, Gandy and Sustainable Terrains developed the Relamp & Relax Program—a sustainability-driven approach to lamp lifecycle management.

The program works on three pillars:

• Procurement: Ensuring access to quality HPS lamps, despite wholesalers phasing them out.
  

• Recycling: Preventing mercury from entering landfills by recycling spent lamps.
  

• Optimization: Testing old LEDs and tracking performance losses to guide replacement timelines.

By incorporating circular economy principles, Sustainable Terrains also supports growers in sustainability reporting and the development of environmental product declarations. Policies like Washington’s 2029 mercury ban make these efforts especially timely. “Relamp & Relax is about helping growers cross the bridge smoothly,” Gandy emphasizes, “not being pushed across by regulation.”

The Next Decade of Lighting Innovation

Asked what the future holds for horticultural lighting in 2030 and beyond, Gandy points to key areas still developing:

• Spectrum tuning: Crop-specific responses to light spectra will guide new production strategies. Blue, red, and far-red ratios will be optimized differently for tomatoes, lettuce, cannabis, and ornamentals.
  

• Automation & AI: Combining spectral data with machine learning enables automated fine-tuning, making lighting a dynamic, data-driven input.
  

• Hardware innovation: Expect modular, integrative lighting structures and new optical designs, such as liquid lenses, to enhance light distribution further.
  

• Power architecture shifts: Transitioning to high-voltage DC systems could reduce infrastructure costs while enhancing reliability.

Practical Advice for Growers Considering LEDs

For growers evaluating the switch, Gandy offers practical guidance:

1. Start small: Run LED trials outdoors or in a single bay to understand the heat balance and make necessary infrastructure adjustments.
   

2. Focus on essentials: Spectrum tuning sounds appealing, but intensity control is often more impactful for plant performance.
   

3. Consider people first: Lighting choices significantly impact worker comfort and safety. Adding a fraction of green light, for example, enhances visibility and crop scouting without incurring significant yield penalties.

In other words, LED adoption is as much about operational functionality as it is about plant productivity.

A Case Study: Lake Huron Project

One of Sustainable Terrains’ latest projects demonstrates these principles in action. In collaboration with Harnois Greenhouses, Brian oversaw the integration of supplemental lighting in Ovaltech freestanding structures near Lake Huron in Ohio.

The first phase of 15,000 square feet was designed around cost-effectiveness, energy availability, and uniformity of light delivery. Early harvests exceeded expectations, lowering the cost per unit of production while demonstrating that the strategic deployment of LEDs can accelerate return on investment. Plans are already in place to triple the number of installations.

Conclusion

Horticultural lighting is now at a crossroads. HPS has served the industry well but is increasingly constrained by regulatory deadlines, sourcing difficulties, and energy inefficiencies. LEDs open the door to nuanced crop management, operational savings, and long-term sustainability, but successful adoption requires a strategic approach, trials, and targeted grower education.

As the industry navigates this transition, experts like Brian Gandy are guiding growers toward solutions that strike a balance between innovation and operational stability. Lighting is no longer a static fixture choice; it is an evolving, data-rich, and sustainability-driven cornerstone of CEA.

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