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

efficient, because the lamp is closer and the light more intense. The farther the lamp is from the garden, the less light plants receive. For example, a 1000-watt reflector with a “hot spot” must be placed 36 inches (90 cm) above the garden. A 600-watt lamp with a reflector that distributes light evenly can be placed only 18 inches above the garden. When placed closer, the 600-watt lamp shines as much light on the garden as the 1000-watt bulb!
    The proper reflective hood over the lamp and reflective walls can double the growing area. Growers who use the most efficient reflective hoods harvest up to twice as much as those who don’t.
    Seedlings, cuttings, and plants in the vegetative growth stage need less light than flowering plants, because their growth requirements are different. For the first few weeks of life, seedlings and clones can easily survive beneath fluorescent lights. Vegetative growth requires a little more light, easily supplied by a metal halide or compact fluorescent lamps.
    Reflective hoods are made from steel sheet metal, aluminum, even stainless steel. The steel is either cold-rolled or pre-galvanized before a reflective coating is applied. Pre-galvanized steel is more rust resistant than cold-rolled steel. This metal can be polished, textured or painted, with white being the most common paint color. Premium hood manufacturers apply white paint in a powder-coating process. Note: there are different shades of white, and some whites are whiter than others. Flat titanium white is the most reflective color and diffuses light most effectively. Glossy white paint is easy to clean but tends to create hot spots of light. Sheet metal hoods are less expensive than the same size aluminum hood, because of reduced materials expense.

The ballast box is attached to the reflector in this greenhouse fixture.

The Wide reflector from Hortilux was one of the first European reflectors to use a deflector below the bulb.

Double fixture greenhouse fixture has the ballasts between bulbs.

This air-ventilated tube is very inefficient, leaving a “hot spot” below.

Place Hortilux 1000-watt fixture 4 feet (1.2 m) above garden.

You can put the Super Wide reflector very close to plants.

This fixture is designed to be mounted next to a wall. It reflects light down and away from the wall.

This Ecotechnics Diamond reflector from Spain is very efficient.

Hortilux sets the standard with their line of reflectors. The Deep model is to be mounted high in greenhouses.

The Adjust-A-Wing is one of my favorite reflectors because it delivers the most light! The deflector under bulb allows it to be super close to plants.

Parabolic dome reflectors orient bulbs vertically. Although less efficient these hoods work well to grow vegetative plants.

Gavita invented a lamp with the reflector inside the bulb! The reflector is the most efficient I have seen!

The Medium reflector from Hortilux is a favorite in Europe.

The Hydrofarm reflector is one of the best values in North America. It reflects a lot of light and “breathes” well.

The “cone” reflector is one of the least efficient available. Much reflected light is wasted.

The Butterfly reflector and deflector is one of the most interesting designs I have seen, but I have no idea about efficiency!

Hortilux Midi reflector spreads light well.

The hammered-finish specular interior of this lamp/ballast fixture diffuses light well.

This vertical reflector is covered in plastic. The bulb hangs between plants.

This reflector from Easy Green has holes for forced-air ventilation and can be placed close to plants.
    The pebble and hammer-tone surfaces offer good light diffusion and more surface area to reflect light. Hot spots are commonplace among highly polished, mirror-like surfaces. Mirror-polished hoods also scratch easily and create uneven lighting.
Horizontal Reflective Hoods
    Horizontal reflectors are most efficient for HID systems, and are the best value for growers. A horizontal lamp yields up to 40 percent more light than a lamp burning in a vertical position. Light is emitted from the arc tube. When horizontal, half of this light is directed downward to the plants, so only half of the light needs to be reflected. Horizontal reflectors are inherently more efficient than vertical lamps/reflectors, because half of the light is direct and only half of the light must be reflected.
    Horizontal reflective hoods are available in many shapes and sizes. The closer the