HID Lamps

HID stand for High Intensity Discharge.  There are two main styles of HID lamps, metal halide (MH) and high pressure sodium (HPS). Traditionally, MH lamps (blue spectra) are used for vegetative growth and HPS lamps (red spectra) are used for flowering. Beyond such spectral or quality of light considerations, HID lamps boast tremendous quantities of lumen output, which equates to deep penetration of plant canopies.  This makes them the go to choice when growing larger plants. This combination of quality and quantity is the reason that HID lamps are often the first choice for most indoor gardeners.