The Spectral Superiority of LED Grow Lights

The techniques for growing plants indoors can vary widely, from sophisticated commercial hydroponic operations that use complex drip irrigation systems to a simple pot of herbs on a kitchen windowsill. What every indoor growing method has in common is the need for an artificial light source that mimics as closely as possible the light of the sun.

It would seem logical that the best light source for growing plants indoors would be as bright and yellow as sunlight appears to the human eye, but this is not the case. The visual perception of the human eye is most acute at the exact center of the visible light spectrum, while those portions of the light spectrum plants need for photosynthesis lie at the upper (blue) and lower (red) ranges of the spectrum. Plants appear green because the pigments in plant tissues absorb light in the blue and red wavelengths and reflect light in the green wavelengths that lie near the center of the spectrum.

In other words, plants do not use most of the light produced by artificial light sources that were designed to allow humans to see in the dark. In a typical incandescent light bulb, only about 30 percent of the light produced can be used by plants for photosynthesis. The same holds true for most fluorescent lights, though some have been tailored to emit light in the Photo synthetically Active Radiation (PAR) spectral range. High-intensity gas discharge grow light systems, such as metal halide or high-pressure sodium lamps, are better at targeting the PAR spectral wavelengths, but still waste about 50 percent of their light output in the central part of the visible spectrum that plants do not use.

All of these issues with the PAR spectrum are why advances in the technology of Light Emitting Diodes (LEDs) over the past 20 years have led to a revolution in indoor horticulture. LED grow lights are engineered to output the exact wavelengths of light best absorbed by the chlorophylls, carotenoids and xanthophylls that are the chief photosynthetic pigments in green plants, which make them the most efficient indoor garden lighting solution from a spectral standpoint.

LED grow lights have many other advantages over traditional lighting sources as well. LEDs can save up to 80 percent on energy-use costs, do not produce any waste heat and can last up to 100,000 hours — more than ten times the device-life rating of other types of indoor garden lights.

Modern LED grow lights are simply the most efficient method of lighting an indoor growing space from any angle.

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