1. METAL HALIDE LAMPS - This type of light is blue-orientated in the spectrum. It is the best type of light to be used as a primary light source (if no or little natural sunlight is available). This type of lamp promotes plant growth.
2. HIGH PRESSURE SODIUM LAMPS - These lamps are red/orange in the spectrum. They are the best lamps available for secondary or supplementary lighting (used in conjunction with natural sunlight). This" type of light promotes flowering/budding in plants. It is ideal for Greenhouses/Commercial growing applications.
3. CONVERSION LAMPS - There are two types:
A. Sodium Lamps which run on halide ballasts - more common.
B. Halide Lamps which run on sodium ballasts.
This type of lamp allows you to tailor the light source to the growth stage of the plant (again using halide blue light for growth and sodium red light for flowering/budding) merely by changing lamps.
4. FLUORESCENT - This type of light is perfect for starts and seedlings but is a poor light source for growth and budding primarily because of low lumen output.
5. INCANDESCENT - Does not require a ballast. These lamps consist of Sylvania Spot Gro R-30 and R-40 flood lamps available in 75 watt and 150 watt. Also good for starts and seedlings. Good lamp for individual plants or small groups of plants. Provides an inexpensive alternative to HID lamps (Halide and Sodium lamps are referred to as High Intensity Discharge Lamps).