Consumers have several options when it comes to choosing a grow lighting system to support the needs of their indoor or outdoor garden. Manufacturers produce several different types of light bulbs that have wide applications in the grow light industry. Each different type of light bulb offers certain features that make them ideal for use during different stages in a plant's development.
Greenhouses and larger indoor plant growth operations traditionally utilize high-intensity discharge (HID) lights because they are capable of producing large amounts of light to shed upon their indoor garden, according to HID Hut. The most popular HID lights are metal halide and high-pressure sodium lights. Fluorescent light bulbs and light-emitting diodes (LEDs) are types of energy-efficient lighting that require a fraction of the power to operate compared to HID lights.
Different types of grow lights are capable of producing different light outputs. Lumens are a measurement that gauges light output. Metal halide lights can produce up to 125 lumens per watt, according to ACF Greenhouses. High-pressure sodium lights can produce 140 lumens per watt, more than any other HID light bulb. Fluorescent lights can produce 39 lumens per watt on average.
LEDs are capable of lasting longer than any other type of light bulb. One LED can last for up to 50,000 hours, according to Tool Base. High-pressure sodium lights can last for up to 18,000 hours, while metal halide lights can last for up to 10,000 hours, according to ACF Greenhouses. According to 1,000 Bulbs, a fluorescent light bulb will only last for up to 10,000 hours before it starts rapidly degenerating.
Almost every type of grow light contains traces of elemental mercury, which is toxic. According to Dark Sky Society, a 250-watt metal halide light bulb can contain upwards of 38 mg of elemental mercury. A high-pressure sodium light bulb of the same wattage can contain around 15 mg of elemental mercury. Fluorescent light bulbs typically contain around 5 mg of elemental mercury, according to Earth Easy.
Color has a large effect on plant growth, which is why certain types of lights are often employed to provide lighting for certain stages of a plant's growth over others. Vegetative growth is promoted under bluish light while flowering is promoted under reddish light, according to ACF Greenhouses. Metal halide lights and fluorescent lights are ideal for promoting growth in all stages of a plant's life because they emit white light, which contains all colors of the visible light spectrum. Fluorescent lights are ideal for promoting growth in seedlings, according to Home Harvest. High-pressure sodium lights emit an orangish glow that can be utilized to promote flowering.