Light emitting diodes, or LEDs, have been steadily gaining acceptance since their introduction within the horticultural community roughly ten years ago. Unlike other lighting technologies used in horticulture, LEDs are a solid state device which makes them extremely durable. LED fixtures usually consist of the panel of LEDs and a circuit board (generally housed within the lighting fixture). Many horticultural LEDs contain a heat sink and/or fan to help dissipate heat and increase the fixture’s life span.
The biggest advantages of LED technology are longevity and the ability to customize the light spectrum. Plants have a heightened response to particular light wavelengths and LED technology has the ability to provide higher amounts of the particular wavelengths plants desire. LEDs are the only technology that has the potential to manipulate the ratio of these wavelengths into the perfect ratio for photosynthesis.
The first few generations of horticultural LEDs were somewhat of a disappointment to the horticultural community because they lacked the intensity to compete with HID lighting fixtures. Many of the original LED fixtures contained only two wavelengths of light (red and blue) and utilized low wattage diodes.
LEDs have made great strides since the first generation and today’s horticultural LEDs have the ability to compete with HID lighting in many ways. Many of the new LED fixtures contain more advanced wavelength ratios along with higher wattage diodes which allow for a greater penetration into the plant canopy. When comparing this technology to HID lighting, coverage is still somewhat of an issue. LED fixtures, unless they contain a special lens, are generally light-directional and the light will not spread out and cover a large area like a HID light. However, LEDs’ higher energy efficiency combined with a lower heat signature has many indoor horticulturists, at the very least, giving LEDs serious consideration. There are also many greenhouse gardeners who have had success using LEDs for supplemental lighting.