Marijuana Horticulture: The Indoor/Outdoor Medical Grower's Bible

lamp travels too far away. Start using the light movers after the plants are 12 inches (30 cm) tall and have several sets of leaves.
    Planter boxes or containers on wheels offer a good alternative to light movers. Containers are rotated daily; wheels make this job a snap. Light reaches every corner of the garden without having to move the lamp. This method has a similar effect as moving the lamp overhead, but is more work because all plants have to be moved, rather than only one or two lamps.
High Intensity Discharge (HID) Lights
    Growers use HID lamps to replace natural sunlight indoors and grow outstanding cannabis. High intensity discharge lamps out-perform all other lamps in their lumens-per-watt efficiency, spectral balance, and brilliance. The spectrum and brilliance of HIDs help growers replicate growth responses induced in cannabis by natural sunlight. Compare charts on HID spectral emission with the chart on photosynthetic response, chlorophyll synthesis, and positive tropism.
    The HID lamp family contains mercury vapor, metal halide, High Pressure (HP) sodium, and conversion bulbs. Metal halide, HP sodium, and conversion lamps have a spectrum similar to actual sunshine and can be used to grow marijuana. Mercury vapor lamps were the first HIDs on the market. Obsolete mercury vapor lamps are inefficient electrically and produce a poor spectrum for plant growth. Now most all mercury vapor lamps have been retrofitted with more efficient HIDs.
    Researchers have created a few better bulbs with a higher PAR rating, but there is no new technology in sight. The latest glass covers of the bulbs have become slightly better at letting light through, but there have been very few major technical advances in these bulbs for the last 20 years.
    Popular HID wattages include 150, 175, 250, 400, 430, 600, 1000, and 1100. A 1500-watt metal halide is also available but is not practical for growing. The 1500-watt lamp is designed for stadium lighting and generates too much heat and light to be used efficiently indoors. Smaller 150-250-watt bulbs are popular for small gardens measuring up to three feet square. Brighter 400-1100 lamps are favorites for larger gardens. The 400 and 600-watt bulbs are most popular among European growers. North American growers favor 600 and 1000-watt bulbs. Super efficient 1100-watt metal halides were introduced in 2000.
    Incandescent bulbs are the least efficient; 600-watt HP sodium lamps are the most efficient. The brightest bulbs measured in lumens-per-watt are the metal halide and HP sodium bulbs.
    Originally developed in the 1970s, metal halidesand HP sodium bulbs were characterized by one main technical limitation–the larger the bulb, the higher the lumens-per-watt conversion. For example, watt for watt, a 1000-watt HP sodium produces about 12 percent more light than a 400-watt HPS and about 25 percent more light than a 150-watt HPS. Scientists overcame this barrier when they developed the 600-watt HP sodium. Watt for watt, a 600-watt HPS produces seven percent more light than the 1000-watt HPS. The “pulse start” metal halides are also brighter and much more efficient than their predecessors.
    High intensity discharge lamps produce light by passing electricity through vaporized gas enclosed in a clear ceramic arc tube under very high pressure. The dose, or combination of chemicals, sealed in the arc tube determines the color spectrum produced. The mix of chemicals in the arc tube allows metal halide lamps to yield the broadest and most diverse spectrum of light. The spectrum of HP sodium lamps is somewhat limited because of the narrower band of chemicals used to dose the arc tube. The arc tube is contained within a larger glass bulb. Most of the ultraviolet (UV) rays produced in the arc tube are filtered by the outer bulb. Never look at the arc tube if the outer bulb breaks. Turn off the lamp immediately. Some bulbs have a phosphor coating inside the bulb. This coating makes them produce a little different spectrum and fewer lumens.
    General Electric, Iwasaki, Lumenarc, Osram/Sylvania, Philips, and Venture (SunMaster) manufacture HID bulbs. These companies construct many bulbs with the exact same technical statistics. According to some gardeners, certain brands of bulbs are better than others because of where they are manufactured. They usually came to this conclusion because they purchased two different brands of (1000-watt) bulbs and had better luck using one brand. What these gardeners