- Metal Halide lamps have output peaks in the blue, green and yellow areas of the PAR spectrum.
- Contains heavy metal vapors and toxic materials, which commonly include mercury, radioactive krypton-85, thallium, dysprosium, thulium, cesium, cerium or other rare earth elements, lead, and asbestos coatings.
- Metal Halide lamps can be prone to exploding.
- “If the arc tube is broken, handling in a well-ventilated area, and local exhaust ventilationor personal protective equipment may be needed” (GE MH MSDS - http://www.batteriesplus.com/msds/GE-METAL-HALIDE.pdf).
- As MH bulbs reach end-of-life, they can require more electricity to produce less light.
- Up to 50% of Metal Halide bulbs may burn out before they reach their lifetime hours rating.
- Long warm-up periods can waste up to 15 minutes of energy consumption per light when first powered.
- For plants to properly flower and fruit they generally require stimulation by the correct balance of red (620-700nm) and far red (700-750nm) light. This is lacking in metal halides and is difficult or impossible to generate even at high power.
- BLUE: The blue output has appearance and plant health benefits including stem elongation inhibition and proper pigmentation stimulation.
- GREEN/YELLOW: Most output is in the yellow-green spectrum, which is the least efficient light region for plant growth. Plants are green because they reflect the most green light rather than absorbing and using it.
- RED: The minimal output in the highly efficient red spectrum results in inefficient overall growth.
Metal Halide Lights
are optimized for human vision, not plant growth.