Lighting is one of the most critical factors in cannabis cultivation, influencing growth, yield, and cannabinoid production. Advanced lighting strategies tailored to each growth stage can optimize plant health and maximize yields. This guide provides detailed techniques for managing light intensity, spectrum, and duration during each stage of cannabis development.
1. Lighting for Seedling Stage
- Light Intensity:
- Provide low-intensity light to avoid stressing young plants.
- Recommended PPFD: 100–200 μmol/m²/s.
- Light Spectrum:
- Blue and white light (400–500 nm) promotes root development and compact growth.
- Light Duration:
- Maintain 18–24 hours of light daily to support rapid establishment.
2. Lighting for Vegetative Stage
- Light Intensity:
- Increase intensity as plants grow larger and stronger.
- Recommended PPFD: 300–600 μmol/m²/s.
- Light Spectrum:
- Blue-dominant light (450–500 nm) encourages leaf and stem growth.
- Light Duration:
- Use an 18/6 light cycle (18 hours light, 6 hours dark) to keep plants in vegetative growth.
3. Lighting for Flowering Stage
- Light Intensity:
- Increase light intensity to maximize bud production.
- Recommended PPFD: 600–1,000 μmol/m²/s.
- Light Spectrum:
- Switch to red-dominant light (600–700 nm) to stimulate flowering and resin production.
- Full-spectrum lights with enhanced red output are ideal for this stage.
- Light Duration:
- Use a 12/12 light cycle (12 hours light, 12 hours dark) to trigger and maintain flowering.
4. Advanced Techniques
- Supplemental UV Light:
- Introduce UV-B light during flowering to enhance trichome and cannabinoid production.
- Use sparingly to avoid plant stress, typically for 2–3 hours daily.
- Far-Red Light for Flower Initiation:
- Expose plants to far-red light (700–750 nm) for a few minutes after the main light cycle to accelerate flowering initiation.
- Dynamic Dimming:
- Gradually increase or decrease light intensity at the beginning and end of each light cycle to simulate natural sunlight transitions.
5. Monitoring and Adjustments
- Measure Light Levels:
- Use a PAR meter to ensure plants receive the correct Photosynthetically Active Radiation (PAR) for their stage.
- Observe Plant Response:
- Signs of light stress include curling leaves, bleaching, or slowed growth.
- Adjust light height or intensity if plants show stress symptoms.
- Optimize Light Distribution:
- Use reflective materials like Mylar or white paint to ensure even light distribution.
6. Choosing the Right Lights
- LED Grow Lights: Energy-efficient and customizable spectrum, ideal for all growth stages.
- High-Pressure Sodium (HPS): Effective for flowering but generates more heat and consumes more power.
- Metal Halide (MH): Best for vegetative growth due to its blue spectrum.