Why Light Quality Matters for Seedling Propagation

Seedling propagation is one of the most critical stages in commercial plant production. The quality of light during the first 2-4 weeks of a plant’s life directly influences root development, stem strength, leaf area, and ultimately the transplant success rate. Unlike mature plants that can tolerate a wide range of light intensities, seedlings are highly sensitive to both light intensity and spectral composition. Too much light causes photoinhibition and bleaching, while too little results in etiolation, weak stems, and poor establishment.

The Koray Lighting GE35 series, originally designed for commercial plant factories and vertical farming, has emerged as an excellent lighting solution for seedling propagation. With multiple models offering different power levels, spectra, and optical configurations, the GE35 platform provides growers with the flexibility to match precise light recipes to different crop species and propagation stages.

GE35 Models Suitable for Seedling Propagation

The GE35 series includes eight distinct models, several of which are particularly well-suited for propagation work. The GE35-60T-F175 (606mm, 30W) is the most compact and gentle option, delivering 535 umol/m2/s PPFD at 0.2m distance. At the recommended seedling distance of 0.35-0.5m, this translates to approximately 150-250 umol/m2/s, which falls squarely within the optimal range for most seedling varieties.

GE35 LED bar installed above seedling propagation rack

The GE35-90T-F175 (900mm, 40W) offers a middle ground with 500 umol/m2/s at 0.2m and Ra greater than 90 for excellent color rendering, allowing growers to visually assess seedling health and identify nutrient deficiencies early. For larger propagation operations, the GE35-120T-F175 (1200mm, 60W) provides 530 umol/m2/s at 0.2m across a full meter of growing space, while the GE35-120-V6 (1200mm, 52W, no lens) offers the highest efficiency at 3.5 umol/J with a broader light distribution pattern ideal for wide propagation benches.

Optimal PPFD Levels for Different Seedling Stages

Different stages of seedling development require different light intensities. During germination (days 1-5), most species benefit from 50-150 umol/m2/s. Once cotyledons expand (days 5-14), the optimal range increases to 150-250 umol/m2/s. For hardening off and pre-transplant preparation (weeks 2-4), seedlings can handle 200-350 umol/m2/s. The GE35 series can be adjusted to meet all these requirements simply by changing the mounting distance.

For example, using the GE35-120-V6 (52W, 370 umol/m2/s at 0.2m): at 0.5m distance, PPFD drops to approximately 100-120 umol/m2/s, suitable for germination. At 0.35m, it delivers about 180-220 umol/m2/s for cotyledon-stage seedlings. At 0.25m, approximately 280-320 umol/m2/s supports vigorous growth in the hardening-off stage. This distance-based adjustment eliminates the need for dimming hardware in many propagation setups.

Spectrum Selection for Propagation

The spectral output of grow light significantly affects seedling morphology. Blue-rich light (400-500nm) suppresses stem elongation and promotes compact, bushy growth with thick leaves. Red light (600-700nm) drives photosynthesis and biomass accumulation. The ideal propagation spectrum balances both regions.

The F175 spectrum, available on the GE35-60T-F175, GE35-90T-F175, and GE35-120T-F175, provides this balance with a full-spectrum white output centered on 450nm blue and 650nm red peaks, with adequate green light for visual inspection of plant health. The V6 spectrum (GE35-120-V6) offers even higher efficiency at 3.5 umol/J with a slightly enhanced blue component that is particularly effective at preventing leggy growth in seedlings. For advanced propagation programs, the GE35-120T-DC-2H-VR features adjustable power output (DC40V/35V, adjustable down to 35W from a maximum of 75W), allowing growers to precisely tune light intensity as seedlings develop.

Setting Up a GE35 Propagation Rack

A typical commercial seedling propagation rack using GE35 components consists of 3-5 tiers of shelving, each 1.2m long and 0.6m wide. For each tier, install two GE35-120 bars (either V6 or F175 spectrum) mounted parallel to each other with 200-300mm spacing between bars. Mount the lights at the underside of each shelf, with the distance to the seedling tray on the shelf below set at 0.25-0.4m depending on the crop.

The compact 38x40mm cross-section of the GE35 housing allows it to fit into tight rack configurations without obstructing tray loading or plant access. The IP64 waterproof rating means the lights can be mounted above misting zones without risk of water damage. At 52W per bar (V6 models), a 5-tier rack with 10 bars consumes only 520W total, compared to over 2,000W for equivalent fluorescent T5HO installations. The AC120-277V universal input with power factor greater than 0.9 ensures efficient operation on standard electrical circuits.

Comparing GE35 to Traditional Propagation Lighting

Traditional seedling propagation lighting typically relies on T5 fluorescent tubes or T8 retrofits. While these provide adequate light distribution, they suffer from several disadvantages compared to the GE35. Fluorescent tubes have a rated lifespan of 20,000-30,000 hours with significant lumen depreciation over time. The GE35 series is rated for 50,000 hours (L70) with minimal light output decline. Fluorescent tubes also contain mercury, requiring special disposal, while the GE35 is RoHS compliant and mercury-free.

In terms of energy efficiency, the GE35-120-V6 at 3.5 umol/J delivers roughly twice the photosynthetic light per watt compared to standard T5HO fixtures (approximately 1.5-1.8 umol/J). This means growers can achieve the same PPFD levels using half the electrical power, or significantly higher PPFD with the same energy input. The GE35-120T-F175 at 60W replaces two 54W T5HO tubes while delivering more uniform PPFD distribution across the growing area.

Conclusion

The Koray Lighting GE35 series is an outstanding choice for seedling propagation in commercial nurseries, vertical farms, and research facilities. With models ranging from 30W to 80W, multiple spectrum options including the versatile F175 and high-efficiency V6, IP64 waterproof protection for humid propagation environments, and energy efficiency that cuts electricity consumption by 50% compared to fluorescent alternatives, the GE35 provides everything growers need to produce strong, healthy seedlings. The 50,000-hour lifespan and CE, RoHS, FCC certifications ensure long-term reliability and regulatory compliance for professional operations.