Artificial Lighting for Indoor Plants | RHS Advice

Artificial Lighting for Indoor Plants

• Purpose: Artificial lighting supplements natural light for winter growth, starting seedlings early, illuminating dark areas, or creating decorative indoor displays.
• Recommended Equipment:
  • T5 High Output (HO) Fluorescent Tubes: The current top choice for home use. They are long-lasting (~20,000 hours), inexpensive, emit little heat, and provide sufficient intensity for growth and flowering.
  • LEDs: Highly energy-efficient and long-lasting with low operating temperatures, though often more expensive to install and may require specialist light meters.
  • Avoid: Standard domestic bulbs (insufficient intensity) and HID lights (excessive heat requiring complex extraction).
• Light Spectrum:
  • Blue light: Stimulates growth and keeps seedlings compact.
  • Red light: Important for growth and flower production.
  • Strategy: Use a combination of red and blue tubes (or Kelvin-rated tubes) to balance development.
• Operational Guidelines:
  • Duration: Typically 16 hours per day.
  • Setup: Reflectors are recommended to direct light downward; a basic setup often involves suspending lights approximately 60cm above plants.
  • Efficiency: Maximize natural daylight first and only use artificial systems when necessary.
• Monitoring Plant Health:
  • Ideal: Mid-green foliage.
  • Too much light: Bleached appearance, stunted growth, or yellow-green foliage. Remedy by moving lights further away, reducing the number of tubes, or shortening the duration.
  • Too little light: Poor growth and dark green foliage. Remedy by moving plants closer to lights or increasing the duration/number of tubes.
  • Imbalanced Spectrum: Too much blue causes stunted, thick-stemmed plants; too much red causes tall, spindly growth.