The following is a professional explanation and actionable advice regarding "What spectrum is needed for seed germination" and "Is full spectrum better?"

I. Core Conclusions

The requirements for spectrum are not high during seed germination; the key factors are temperature, humidity, and substrate moisture. Most crops can germinate under low light or even darkness.

Once the cotyledons unfold and the seedling stage begins, a spectrum with a higher proportion of blue light is more conducive to compact plant growth and robust seedlings.

Full spectrum white light is generally a universal and user-friendly choice, facilitating a direct transition to the vegetative growth stage; however, if only germination/seedling cultivation is targeted, a spectrum with enhanced blue light is preferable.

II. Key Spectral Points

Blue light (approximately 450 nm): Promotes short and robust seedlings, thicker leaves, and stomatal development, reducing etiolation. Moderately increasing the proportion of blue light is beneficial during the seedling stage.

Red light (approximately 660 nm): Promotes growth rate and biomass accumulation, but seedlings are prone to etiolation under red light alone; it needs to be combined with blue light.

Far-red (approx. 730 nm): Can trigger morphogenesis (elongation), generally not needed excessively during germination; use with caution to avoid weak seedlings.

UV-A (365–405 nm): Not essential for germination, excessive intensity may cause stress; if used to improve seedling resistance, control intensity and duration.

Full-spectrum white light (including 400–700 nm): Covers the visible range, good color rendering, easy to use, suitable as general seedling light.

III. Intensity and Photoperiod Recommendations (General Reference)

Germination period: Many crops can germinate in darkness or at very low PPFD; if light is provided, maintain low to moderate intensity.

Photosynthetically active radiation intensity: Approx. 50–150 μmol/m²/s

Photoperiod: 12–16 hours/day

Seedling stage (after cotyledon expansion): Increase the proportion of blue light or use full-spectrum white light, avoid excessive light intensity causing dryness or scorching.

PPFD: Approximately 150–300 μmol/m²/s (leafy vegetables/herbs); fruit vegetables can reach 200–400 μmol/m²/s.

Photoperiod: 14–18 hours/day (depending on the crop).

Distance: Generally, keep the lamp 30–45 cm away from the seedling surface, adjusting slightly according to leaf condition; if etiolation occurs, slightly reduce the distance or increase blue light/decrease power.

IV. Should Full Spectrum Be Selected?

If your process involves using the same lighting throughout germination—seedling cultivation—vegetative growth, full-spectrum white light is more practical and easier to operate.

If you are specifically creating a "seedling tray area" and want shorter, sturdier seedlings with compact internodes, you can choose a spectrum of "enhanced blue light + appropriate amount of red light".

For commercial seedling cultivation, high color rendering full-spectrum white light with adjustable red and blue channels is often used for flexible control.

V. Supporting Environment and Management are Crucial

Temperature: The optimal germination temperature for most vegetables is 20–25 ℃; too low a temperature affects the germination rate, while too high a temperature easily leads to etiolation.

Humidity and Moisture: Keep the substrate evenly moist, avoiding alternating periods of waterlogging and drought; relative humidity of 60–80% is common.

Ventilation and CO₂: Light ventilation reduces mold and damping-off disease; ensure air circulation.

Light Uniformity: Seedling trays should have as uniform an illumination as possible to avoid uneven seedling emergence due to weak light at the edges.

VI. Quick Selection Recommendations

For germination only: Low-power full-spectrum or bluish strip/panel lights, with PPFD controlled at 50–150 μmol/m²/s.

For germination to seedling integration: Full-spectrum panel lights (4000–5000 K) + dimming, with power increased appropriately later.

For more professional use: Choose lights with independent blue/red channels; increase the blue light proportion to 20–30% during the seedling stage, with red light as a secondary element.

If you can provide the specific crop (e.g., tomato, pepper, leafy greens, succulents, or flowers), seedling tray specifications, area, and existing light fixture parameters (PPF, power, size), I can provide you with precise spectrum and intensity settings, light spacing, and photoperiod solutions. I can also estimate the expected improvement in electricity costs and seedling uniformity. Additionally, if needed, we can compile a "Seedling Light FAQ and User Guide" for customer use in training or product pages.