Medical Cannabis Cultivation Methods

Medicinal Cannabis Cultivation Methods: Indoor vs. Outdoor

A grower tends to his cannabis field.
A grower tends to his cannabis field.
Jupiterimages/Getty Images

Successfully tending a cannabis garden -- whether indoor or outdoor -- requires the identical six key ingredients [source: Cervantes]:

  • Light
  • Air
  • Water
  • Nutrients
  • Heat
  • Growing medium (i.e., soil, smooth gravel)

The appropriate cultivation method depends on the resources at a grower's disposal and the desired harvest. For instance, large-scale growers in Humboldt County, California, have more legal liberty to tend expansive outdoor plots, whereas an amateur medicinal grower in Arizona might opt for a minimal basement grow room.

Standard indoor cultivation: Cannabis naturally blooms once per year, but since it's a photoperiodic-reactive plant, growers can intensify interior light exposure to stimulate faster bud development. With each plant nestled in its own 3-gallon container full of moisturized soil, the growing marijuana plants require between 16 and 24 hours of continual fluorescent light exposure per day for roughly two months [source: Weed Farmer]. Due to heat output from such intensive lighting, the grow room -- generally a well-insulated basement, closet or attic -- may need a cooling fan to keep temperatures near the optimum 70 degrees Fahrenheit (21 degrees Celsius) [source: GreenMansPage].

Standard outdoor cultivation: Climate control is one of the greatest challenges for mastering indoor medicinal marijuana cultivation, but many of those controls fly out the window when the operation moves to the great outdoors. Growing medicinal marijuana outside exposes it to unpredictable weather, as well as more pests, mold and other harmful pathogens. To give the crops the best chance to thrive, outdoor growers should tailor the cannabis strain to their hardiness zone [source: Cervantes]. Growers in Oregon, for instance, would want to look out for strains suitable for cooler, wetter climates that tend to attract more fungal growth. Those horticultural standards will guide the specific soil treatments and water supplies necessary for farming the marijuana plants.

On the one hand, free sunshine can save a bundle, but on the other hand, growing outdoors could pose more imminent legal threats since it's harder to hide from a law enforcement helicopter. For that reason, it's doubly important to abide by the letter of state legalization laws -- although under the federal Controlled Substances Act, which criminalizes marijuana cultivation, authorities can still prosecute growers large and small [source: PBS Newshour].