Many types of lights can be used for growing plants indoors. Florescent lights provide sufficient light for small plants and seedlings, but once the plants grow larger a more powerful light is needed. Metal halide lights provide an intense light spectrum similar to the sun's rays. Since halide lights are so powerful, fewer are needed to supply light to plants.
Determine the wattage of light bulb to purchase for the light. The wattage is based on the size of the grow space and whether any additional sunlight is present. The Resources section contains a link to help estimate the needed bulb wattage.
Use the light manufacturer's instructions to attach the light to a shelf, board or ceiling above the plants. Most halide lights are attached by inserting screws through the base with a screwdriver.
Keep at least 1 foot between the light and the top of the plants. Any closer, and the light will burn the plant leaves.
Place a thermometer directly beside the plants and under the light. Monitor the temperature on a regular basis to ensure that the light is not too hot. If the temperature goes above 90 degrees F, change to a lower wattage bulb or place the plants farther away from the light.
Install proper ventilation. If the grow space is small, such as a grow closet or small shed, install a bathroom exhaust fan in the room for proper ventilation. This prevents the temperature from rising too high. If the lights are installed in an open room, ventilation is not necessary.
Plug the light into an ordinary lamp timer and insert the timer into an electrical socket. Set the timer to run lights for six hours a day.