At present, there are at least 8 different types of light commonly used for gardening. The below list will attempt to ‘shed some light’ on the differences between them:
FLORESCENT – Standard florescent bulbs which can be found in practically every home and/or office can be used to grow plants, but due to limited broadcast must be placed 1”-3” above the plant(s) and work best for seedlings and cloning.
T5 / T5HO – T5 is a high output fluorescent which puts out 3-4x the PPFD as standard, and the T5HO puts out 2-3x as much as a T5. These both come in varying color temperatures and can be used for growing plants full cycle with a minimum of heat and energy, time and yield are the sacrifice however.
HID – High Intensity Discharge or HID grow lights have been the standard for 40 years. They come in two distinct types…
MH – Metal Halide which provide a blue temperature which is best suited for vegetative growth, and
HPS – High Pressure Sodium which produce more of a red spectrum best utilized by flowering plants.
HID grow lights have traditionally been magnetic, built with coil windings and condensers but more recently have become available as digital, built with circuit boards and computer chips, which help to keep heat down.
DE – Double Ended are actually a type of HID which operate more efficiently. Though only available for the last few years, they have quickly become the standard as growers have seen yields increase of up to 30%.
CMH – Ceramic Metal Halide is kind of a hybrid of MH and HPS technology, utilizing a ballast and and arc bulb. The difference, aside from less power consumption, is in UV-B radiation which both HPS and MH are lacking, even when used together. Some growers claim this beneficial UV-B light increases your plant’s terpene profile.
LED – Light Emitting Diode is technology which utilizes semiconductor diodes which glow when voltage is applied. Although this technology is fairly recent to grow lighting, it looks to have a very promising future. LED’s are available in dozens of different color spectrums, shapes, sizes and applications.
LEP – Light Emitting Plasma is among the newest contender in lighting technologies, providing a robust PPFD as well as a full color spectrum the technology seems propitious.