HPS grow light, or High Pressure Sodium lights are classified in a group called HID or High Intensity Discharge lighting.
HPS lights are used during the flowering or budding time of growth in a plants life this is due to the spectrum of light that is given off by theses types of grow light systems.
HPS or High Pressure Sodium bulbs give off the red or orange glow that could be compared to the harvest sun it has been said that this particular light spectrum enhances density and volume of the crop this could be due to the increased stimulation of the floral hormones.
These lights have a life span twice that of metal halides but after 18,000 hours of use they will start to draw more electricity then there rated watts while gradually producing less light. HPS bulbs produce up to 140 lumens per watt making. This type of lighting most popular among growers around the world due to the high lumen output.
HPS grow lights lack in the blue light spectrum it is not advised that you try to start a young plant under an HPS grow light due to the fact that your plant will try to grow towards the light source causing it’s stem to stretch and weaken this will make it hard for the plant to hold its buds or flowers later on in its life.