Indoor gardening, including hydroponic gardening, is a popular way to garden during cold winters. Even if you have a greenhouse, your winter plants could benefit from supplemental lighting. The type of light that will work best will depend on whether you are growing green, leafy plants or flowering plants. The best type of light will also depend on the availability of natural light.
Select the best lighting for your needs. High Intensity Discharge (HID) lights produce the most light per watt of energy consumed. There are two types of HID lighting: Metal Halide (MH) and High Pressure Sodium (HPS). MH lights produce more light in the blue spectrum and are better for green, leafy plants. MH lights are better if HID lights are the only source of light. HPS produces more light in the orange and red spectrum. These lights encourage flowering, but need some supplemental sun. HPS lights are best used in existing greenhouses that get some natural sunlight.
Install the lights 2 to 3 feet higher than the expected height of the plants. If the plants touch the light, they can be damaged by heat. Most lights are hung from chains that attach to the ceiling, thus allowing for adequate air space for cooling between the fixture and the ceiling. The chains also allow you to adjust the height of the grow lights based on what you are growing.
Leave the lights on for 10 to 12 hours for most vegetables. Flowers may do better with 16 hours of light.