Growing Cannabis Indoors vs. Outdoors vs. Greenhouse | The Great Debate

People have practiced cannabis cultivation for a millennium, and as with most crops, cannabis farming traditionally occurred outdoors. Starting with Reefer Madness in the 1930s and compounded by the War on Drugs in the 1970s this amazing, diverse naturally growing plant was made illegal. Did you know that the US government classifies marijuana as a Schedule 1 drug, which is classified as something that has no currently accepted medical use and a high potential for abuse, along with other drugs like heroin, LSD, and ecstasy? Did you also know that drugs like cocaine, methamphetamine (seriously meth!), and oxycontin are classified as safer? When the War on Drugs intensified during the Reagan Administration, growing indoors became a viable option for domestic cannabis cultivation largely because prohibition drove up prices. Combined with cannabis growers developing new strains, new methods emerged to give growers complete control over their product. These high-tech indoor cultivation operations have produced the best-looking cannabis in history. Finally, in the 21st century, the public perception of cannabis is quickly changing in favor of legalization. With these new growing methods available, the question becomes, which growing method is best? Indoors, outdoors, or in a green house? Most think it’s a no-brainer; if you want to grow the best cannabis, you grow it indoors, right? Well, it’s more complicated than that. Let’s get into it.  


Benefits and Drawbacks Of Different Cannabis Growing Methods


Quality Control


Proper temperature, humidity, and light intensity are critical to producing high quality cannabis. One of the key benefits of growing cannabis indoors is the ability to control these environmental conditions. Outdoor cannabis farming is subject to the whims of nature ‒ too much wind, too much rain, hail, frost, humidity and so on. Indoor cannabis farming provides growers with the ability to completely control these environmental factors.


Growing marijuana indoors


This level of control enables indoor growers to achieve optimal conditions for growing cannabis plants, which produces beautiful flowers, often with higher THC levels than cannabis grown outdoors. Also, the ability to control the light cycle indoors allows for multiple harvests annually, while generally outdoor cannabis farms are limited to one harvest per year. Depending on location, outdoor cultivation can provide optimal environmental conditions for premier cannabis quality. Places like the emerald triangle, Southern Oregon and Northern California, are world renown for warm, dry summers, that create a cannabis quality that rivals the best indoor facilities. The sun provides a light spectrum that is unmatched with current indoor lighting technology that in some instances can increase terpene development that enhances the natural flavors and aromas of the cannabis.  


High Costs for Farmers


The main drawback of indoor cannabis cultivation, is the cost. Farmers have to deal with pests, power, and control the environmental factors to produce an ideal growing environment. The capital costs of an indoor facility can be up to 10x higher than an outdoor farm. Done right, indoor buildouts can cost upwards of $100/ sq ft.,  while an acre of outdoor cannabis, approximately 40,000 sq. ft., can be constructed for as little as $15 to $20 per square foot. Cultivating cannabis indoors always costs more than growing outdoor.


Marijuana grown outdoors in the emerald triangle of Southern Oregon


The biggest indoor operating cost, is the electricity to produce a sufficient amount of light and then the cooling required to remove that heat in order to grow healthy cannabis plants. To imitate the sun, large, powerful, energy-hungry lights must be installed and run on a consistent schedule. A byproduct of all that light is heat. Each of those lights, generate significant amounts of heat that if not cooled properly raise temperatures in the room that will destroy or severely lower the quality of the cannabis. These two items are the largest operating costs associated with indoor cultivation that are not seen with outdoor farming. Introducing CO2 to increase indoor cannabis yields adds yet another cost. These are costs that are never incurred by outdoor cannabis farmers, making outdoor cultivation more cost-effective as well as more sustainable.  


Pests are A Problem


Pest control ranks as one of the top concerns that requires very robust integrated pest management (IPM) solutions. While an outdoor cannabis farm must withstand more severe environmental conditions, it also benefits from natural checks and balances that limit pest infestations. Insects like aphids and mites, especially spider mites and russet mites, can spell doom for an indoor cannabis farm. On the other hand, outdoor cannabis cultivation benefits from natural predators like ladybugs, ants, and wasps. Wind and rain also help keep insect pests from running rampant outdoors. Mold and mildews, especially botrytis (bud rot) and powdery mildew, are equally problematic for indoor and outdoor growing methods. If not properly controlled, they can destroy an entire cannabis crop. Quite simply – with indoor cultivation methods pests, molds and mildews can spread rapidly and devastate an entire crop within days due to the contained nature of the facility. With outdoor cultivation, there are better natural controls for IPM but depending on weather and relative humidity, botrytis is almost impossible to control. Even if successfully managed, these pest issues represent additional time and effort on the part of the cannabis farmer. Throw in heightened concerns about the harmful effects of pesticide-tainted cannabis, and it’s easy to see why many cannabis cultivators readily opt for an outdoor cannabis farm.  


Greenhouses Are An Excellent Alternative


While the answer to the indoor-outdoor debate will vary among cannabis farmers depending on the factors mentioned here, the best all-around approach to cannabis cultivation may lie somewhere in the middle. In this case, the middle ground is greenhouse cultivation, which combines many of the best factors from indoor and outdoor cannabis farms.


Medical Marijuana Farm Greenhouse Full of Mature Plants Ready For Harvest


Like outdoor cannabis farming, greenhouse cultivation benefits from free sunlight. Like indoor cultivation, a greenhouse grow eliminates crop damage from wind, rain, and hail. At the same time, a greenhouse gives growers a significant degree of environmental control and extends the natural growing season. By adding heat to the greenhouse, cannabis cultivators can grow plants year-round even in cold climate zones, and employing natural gas or propane heat increases CO2 levels, providing an ancillary benefit. Of course, as with any gas-fired appliance, a carbon monoxide detector should be installed to ensure health and safety.  


Lighting for Growing Cannabis


Since cannabis flowering depends upon the length of the daily light cycle, or photoperiod, growing cannabis year-round in a greenhouse requires additional considerations beyond temperature and humidity. To flower cannabis plants during the longer days of summer, cannabis growers must equip their greenhouses with light deprivation (or blackout) curtains to ensure the 12 hours of darkness required to induce flowering. On the other hand, keeping plants in the vegetative stage of growth during the other three seasons requires supplemental lighting to maintain a preferred light cycle of 18 hours of light and six hours of darkness. While this supplemental lighting adds to the cost of producing cannabis flowers, the supplemental lights of a greenhouse grow are used only when necessary. This results in a significant cost savings compared to indoor cannabis cultivation. Unlike indoor lighting, which increases cultivation costs by requiring some type of cooling system, supplemental greenhouse lighting is used primarily during cooler seasons when the lights’ heat emissions are actually beneficial.  



So Which Cultivation Method is the Best?


So, is there a winner in the outdoor-indoor-greenhouse debate? The answer is, “Yes.” But the best approach to cannabis cultivation depends on variables unique to each grower.  Are you located in an area that has the correct climate and are looking for the least expensive, and most sustainable approach to growing cannabis? Grow outdoors.  Do you want the most consistent, reliable, and highest level of control regardless of cost and time commitment? Grow indoors.  Do you want to strike a balance between these two extremes and still attain consistent results? Grow in a greenhouse. At Grown Rogue, we employ all these methods in our cannabis production. Our decision is based on the unique characteristics of our strains and what we are trying to accomplish with the end product. We strive strike a balance between cost, quality, and purpose, ensuring that each unique strain is being grown in its ideal conditions with the lowest overhead costs. This ensures we are creating quality products at competitive pricing. On a final note, the importance of operating a personal cannabis grow within the requirements of the law cannot be overstated. In Oregon, adults can grow a maximum of four plants per residence, regardless of how many people live at the residence. Please remember to follow all local and state laws when considering which growing method may be right for you.   Happy growing!


One Response

  1. Looking to establish medicinal cannabis farm in Australia. Need good seed_stock, good planning framework, help with setup and investor. Have secure land and water but it’s in cold area. The article seems to suggest greenhouse would be the best system?