TYPES OF GROW LIGHTS FOR HYDROPONIC PURPOSES

Natural light is optimal for encouraging hydroponic plant growth, but growth can also be accelerated by the use of artificial lighting.  The use of “grow lights,” as they are called, effectively extends daylight for the plants (or substitutes for daylight altogether). Because plants need a certain amount of intensity of light and draw from the full light spectrum for various stages of growth, standard incandescent lights don’t work well as grow lights. (Consider that you need to emulate sunlight as much as possible.)  Typically, hydroponic plants do well with High Intensity Discharge (HID) bulbs, two of which are listed below.  Along with the two HID bulbs, here are the types of bulbs most regularly used for hydroponic growth.

Metal Halide Bulbs (MH)
Arguably the most popular HID-type bulb, metal halide bulbs produce the closest emulation of summer sunlight available, and yield the spectral colors plants thrive on most—especially the blues, which encourage vegetative growth.  MH bulbs tend to die out gradually and need to be replaced before they actually burn out, because they eventually do not yield enough lumens to help the plants anymore.  However, MH bulbs are long-lasting, and can usually function for a year or more (typically 10,000 hours) before having to be replaced.

High Pressure Sodium Bulbs (HPS)
The other HID-type bulb, the high pressure sodium bulb is best suited for supplementary lighting, used together with natural sunlight.  HPS bulbs emphasize the orange-red band of the spectrum, which is good for flowering plants.  These grow lights are less expensive than metal halide, and longer-lasting (typically 18,000 hours). However, because they are deficient in blue light, HPS bulbs are not usually recommended as a replacement for natural light, nor as an alternative to metal halide.  They’re best suited for a greenhouse environment.

Fluorescent Bulbs (CFL)
Where in earlier days fluorescent light bulbs were not intense enough, these days fluorescents are made that have enough lumens to supply light for hydroponics.  This can be done either with high-output tubes or with larger quantities of lower-output tubes.  Fluorescents emit much smaller amounts of heat than HID bulbs, which means they can be placed much closer to the plants—and when they are placed closer (but not too close), they emit enough of the spectral colors to promote growth.

LED Grow Lights
The newest version of grow light, the advantage of LED bulbs is that they are comparable to the output of a high pressure sodium bulb while being extremely energy efficient, and emitting almost no heat.  The disadvantage is that they are expensive and promote slower growth.  In fact, it can be argued that the same growth results can be achieved with fluorescent grow lights, which are far less expensive.  So while they are the newest thing, the jury is basically still out on whether LED bulbs will be the wave of the future for grow lights.