As winter approaches, cannabis cultivators' thoughts turn to indoor growing-and the host of factors that determine whether a garden tended inside can rival the great outdoors.

Growing indoors requires artificial lighting. Typical fluorescent lights are usually cheap, plentiful and easy to find, but may not provide enough lumens for serious bud production. I've seen evidence, however, of cannabis flowers thriving under the new breed of compact fluorescents and special horticultural units with banks of T8 bulbs. For those with concerns about heat or high electricity usage, these lighting alternatives may very well be the only option.

For optimum use of space, high-intensity discharge (HID) lighting is necessary. Whether you use high-pressure sodium (HPS) or metal-halide (MH) bulbs and ballasts, yields increase greatly under horticultural HID lighting.

Determining the wattage of the lighting you choose depends on the size of your space and any limitations on heat exchange. Remember that pot plants need 40 to 50 watts per square foot to thrive and reach full potential.

Approximate Lighting Requirements
250-watt HID for a 2' x 2' space.
400-watt HID for a 3' x 3' space.
600-watt HID for a 4' x 4' space.
1,000-watt HID for a 5' x 5' space.