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SOLUTIONS

Cucumber

Grow Lighting

Background: The Evolution of Greenhouse Cucumber Lighting

Supplemental lighting is essential for year-round cucumber production, particularly in northern climates where winter daylight is insufficient for acceptable yields . The industry is rapidly transitioning from High-Pressure Sodium (HPS) lamps to Light-Emitting Diodes (LEDs) due to superior energy efficiency, longer lifespan, and the ability to tune light spectra.

This shift is not simply a lamp replacement—it represents a fundamental change in greenhouse climate management. LEDs emit very little radiant heat compared to HPS lamps, creating a new growing environment with different temperature, humidity, and plant transpiration dynamics.

Background: Key Advantages of LED Lighting

  • Higher light intensity without excess heat: Growers can achieve photosynthetic photon flux densities (PPFD) of 275 μmol/m²/s or higher—approximately a 50% increase over HPS—without overheating the facility .

  • Spectral control: Different wavelengths can be manipulated to influence plant morphology, photosynthesis, and fruit quality .

  • Energy efficiency: Combined with dehumidification systems, LED installations can significantly reduce heating energy consumption .

Background: The Science of Light Spectrum for Cucumbers

Cucumbers react strongly to spectral composition:

  • Red light (660 nm) is most efficient for photosynthesis and, when combined with far-red, influences stem elongation and leaf expansion .

  • Blue light (450 nm) regulates stomatal opening, promotes compact growth, and affects photomorphogenic responses .

  • Far-red light (730 nm) is critical for maintaining proper leaf morphology and plant vigor, particularly during low-light winter periods .

  • Green light penetrates deeper into the canopy and contributes to overall photosynthesis .

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Challenges: LED-Lit Tomato Production

The transition to LEDs introduces several physiological and environmental challenges that growers must actively manage.

Challenge Area
Description
Primary Consequences

Solutions and Best Practices

Addressing the challenges of LED lighting requires an integrated approach combining climate control, spectral management, and cultivar selection.

1. Managing Climate and Transpiration

Active Dehumidification Systems
Instead of relying on pipe heat and opening vents (which wastes energy), mechanical dehumidification systems actively remove moisture from the air. This allows screens to stay closed for energy savings while controlling humidity . Norwegian grower Kristian Solberg notes: "With a dehumidification system, we can close the screens and insulate more without stressing the crop" .

Strategic Heating Placement
When transitioning to LEDs, heating strategies must be reversed. Under HPS, rail pipes were primary heat sources; under LEDs, overhead pipes near the roof become primary to warm the crop head and drive transpiration .

Air Circulation
Air movement is critical for cucumber crops. Vertical fans disrupt boundary layers around leaves and ensure uniform climate throughout the canopy, preventing pockets of high humidity .

2. Refining Lighting Strategies

Ensure Adequate Far-Red Light
Far-red is essential during low natural light periods to maintain proper plant morphology. Growers who initially omitted far-red observed leaf curling, shorter petioles, and reduced vigor. Adding far-red at appropriate levels (typically 6-9% of spectrum, adjusted dynamically) restores normal growth .

Dynamic Spectrum Management
Modern LED systems allow real-time spectral adjustments:

  • Far-red modulation: Gradually reduce far-red percentage as natural light increases .

  • Blue supplemental morning lighting (B-SML): Two hours of 100% blue light (10 μmol) before the main photoperiod improves photosystem II efficiency and stomatal conductance, enhancing physiological readiness for the day .

Consider Inter-lighting
LED inter-lighting within the canopy delivers light to lower leaves, improving overall light use efficiency. Research shows inter-lighting increases fruit weight and quality parameters including color, dry matter content, soluble solids, chlorophyll, vitamin C, and storage properties .

Explore Continuous Lighting (CL) Strategies
Recent research demonstrates that mini-cucumber cv. "Bonwell" can tolerate continuous light (24 h) without yield reduction when using spectral manipulation. Continuous red/blue light or alternating red/blue strategies maintained yield, chlorophyll concentrations, and photosynthetic capacity comparable to 16 h photoperiods .

3. Cultivar Selection and Testing

Given the dramatic cultivar-specific responses to LED lighting, selection is critical:

  • Some cultivars like 'HiLight' show only 5% yield reduction under LED top-light, while 'DeeRect' dropped 35% .

  • 'Hi Lumiere' showed stronger performance and light use efficiency than 'Uptrace' under dynamic FR strategies .

  • Growers should trial multiple cultivars under their specific LED setup before committing to large-scale transitions.

4. Minimizing Structural Shading

Fixture Design Innovation
Newer LED fixtures are designed specifically to reduce shadow-related light losses. The CoolStack PRO 2026 series, for example, uses advanced heat pipe and stack-fin technology to miniaturize fixtures without compromising output, reducing the permanent shadow footprint .

Strategic Fixture Layout
Consider fixture placement to minimize interference with natural sunlight penetration, particularly during midday when solar radiation is highest.

5. Innovative Energy-Saving Strategies

Pulsing Light and Twilight Simulations
Research at KU Leuven is exploring:

  • Slow pulsating light: Long light pulses (10-20 s) alternating with short dark pulses (1-5 s) to mimic natural cloud shadows

  • Twilight simulation: Gradual switching on/off of LEDs at natural sunrise/sunset rhythms

These strategies could save 10-20% electricity without compromising crop quality or yield .

6. Nutrient Management Integration

While specific cucumber nutrient studies under LEDs are limited, the principles from tomato research apply: reduced transpiration affects calcium transport, and LED-grown crops may require adjusted nutrient ratios. Monitor for deficiency symptoms and adjust feed accordingly.

Summary of Key Research Insights

  • Far-red light is essential: Cucumbers require adequate far-red during winter months to maintain normal leaf morphology, petiole length, and plant vigor .

  • Cultivar selection is critical: Yield responses to LED lighting vary dramatically between cultivars—some lose 35% yield, others only 5% .

  • Dehumidification enables LED success: Active humidity control allows screens to remain closed for energy savings while preventing crop stress .

  • Dynamic lighting improves outcomes: Spectral adjustments throughout the day (blue morning pulses, far-red modulation) enhance plant performance and energy efficiency .

  • Inter-lighting boosts fruit quality: LED inter-lighting increases fruit weight and quality parameters including vitamin C and soluble solids .

  • Continuous lighting is possible: Some cucumber cultivars tolerate 24-hour lighting with appropriate spectral management, potentially reducing capital costs .

  • Shading matters: Permanent LED fixtures create continuous shadow that directly impacts profitability—choose low-profile designs .

Practical Recommendations for Growers

Consideration                       Recommendation

Starting point                        Install active dehumidification before or alongside full LED conversion

Spectrum selection            Ensure adequate far-red (6-9% minimum) during low-light periods

Cultivar testing                     Trial multiple varieties under your specific LEDs before full commitment

Climate strategy                  Use overhead pipes as primary heat source to drive transpiration

Light distribution                 Consider inter-lighting to improve lower canopy light penetration

Dynamic control                   Implement dawn blue pulses and far-red modulation based on natural light

Fixture selection                  Choose low-profile fixtures to minimize permanent shading

Case Study

Project name

Electricity Before & After
To accelerate the transition from traditional agriculture to industrialized agriculture.

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Gas Before & After
Each grower has access to right mindset, data, tools and equipment for a more sustainable and profitable agriculture.

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Yield Before & After

Quality, value & integrity

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