Where’s a better environment to grow weed: indoors or outdoors?

Published on June 18, 2020 · Last updated July 28, 2020
cannabis growing, indoor cannabis, outdoor cannabis
(Ian Miller/AdobeStock)

The fight over whether indoor farming is better than outdoor has raged for decades. It is normally framed as outdoor idealists against indoor advocates. There are obvious benefits to both grow methods—free light and cheap land versus control and consistency—and greenhouses offer some of both. But now, the debate has moved into the new zone of commercial farming.

Legalization in both North and South America has altered the cannabis game. In the past, cannabis production primarily occurred indoors and out of sight, but today, furtive fields have been transformed into big agriculture and commercialism has changed the discussion. For companies, the indoor versus outdoor question is less about principles and more about profit.

The broad answer for both hobby growers and large companies remains the same: it depends. The specific answer is different for everyone.

Factors to consider: price, climate, and quality

“Which is better really depends on what aspect you look at,” said Ed Rosenthal, a well-known cannabis expert, author, and advocate. “It really depends on your situation.”

Climate is a factor for both commercial and hobby gardeners, explained Rosenthal. Plants need sun and warmth to thrive. Latitude makes a difference in daylight hours and length of grow season. Living situation also plays a part. If you’re in a city or worry about your neighbors, indoors would make more sense, Rosenthal said.

Indoor allows you to completely control your environment, including temperature, light source, CO2 levels, and humidity, without having to worry about weather. Indoor typically produces flower with higher THC percentages.

And cost matters. Outdoor farms require far less investment. Low-value land can offset a smaller crop or a shorter season. Free sunlight and free soil are more than just pennies saved, but growers are exposed to natural risks, said Rosenthal, who now works as a consultant. “It goes both ways outdoors.”

With advances in outdoor farming, a lot of drawbacks can be mitigated no matter where you live. And no light bulb can produce the same spectrum as the sun. Some argue that although outdoor flower may not look as pretty as indoor, the taste, effects, and aroma are better.

Growing weed outdoors

Surprisingly, outdoor can be a better choice in a cold, wintery clime.

One of Rosenthal’s recent consulting projects was an outdoor farm in arctic Canada. He said. The growing season is three months long, which means only one crop. There’s a low yield per acre and the plants have mediocre THC levels. But none of that matters to those farmers. With 200 acres of dirt cheap land and an end product of concentrate instead of flower, they can get a high profit with minimal investment.

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The ultimate factor is the goal, Rosenthal said. If you want a certain grade of cannabis, such as a gorgeous, stanky dried flower with a consistent quality, indoor could be better in spite of the upfront and maintenance costs.

The key mistake, according to Rosenthal, is not adapting to today’s legal climate. Prohibition era thinking persists, keeping the fallacy alive that a larger plant is better. Small, single stem plants can produce more flower, while larger plants spend more energy on growing stalks and leaves. Gardening is really all about the harvest, said Rosenthal, so that’s wasted energy.

“You really have to look at it more agriculturally. And from what I’ve seen a lot of large companies haven’t,” said Rosenthal. “Yet.”

Indoor growing

Canadian company Organigram has similar core principles. Its gardeners are focused on an end goal—plants for profit—and are constantly trying to improve grow methods.

“We respect the plant. But it’s also just a widget,” said Matt Rogers, Organigram’s Senior Vice President of Operations.

When the Canadian market opened up a few years ago, Organigram took the long view, said Rogers. Other companies were racing to market, going for cheap, high capacity, and Organigram saw a huge opportunity to differentiate. “Quality will win,” said Rogers. “We’re growing the athletes that are going to the Olympics, so to speak.”

Organigram spent CA$250 million constructing its facility, Rogers said. It contains over a hundred grow rooms, each of which can be tailored to the specific climate needs of a varietal.

The design of those rooms was carefully tested to ensure roof-to-ceiling and corner-to-corner consistency of temperature, humidity, CO2 levels, and light, among other things, said Rogers. Each room can produce five crops a year, resulting in about 500 crops annually and a staggering possibility of 100,000 kilos (~220,000 lbs) of market-ready marijuana.

“Data has made a lot of good decisions for us,” said Rogers. “It’s about the little things that add up to the big things.”

Those little things are informed by experiments performed in the research and development grow rooms, which hold five to fifteen trials at a time. One experiment revealed that a room with 70 wider-spaced plants produced the same yield as 100 plants, a dramatic difference to cost over 100 rooms.

Outdoor has its place and nature has a million benefits, Rogers said. But customizable, indoor rooms and evolving technologies are what suit Organigram’s purpose: consistent high-quality dried flower.

Like Rosenthal, Rogers espouses goal-oriented farming. “Don’t just grow cannabis, grow cannabis for a specific reason.”

The best of both worlds: hybrid farming

A continent away, Plena Global’s goal is to produce cannabinoid ingredients for the pharmaceutical industry. They chose a location accordingly—it’s a Canadian company, but its outdoor farm is in South America.

“The advantage to outside is cost, right off the bat,” said Richard Zwicky, Plena’s founder and CEO. Outdoor farming in general is more difficult, he acknowledges, but Plena’s production costs come in at less than 20 cents a gram.

This is due in no small part to the fact that Plena’s farm is in Columbia. It is situated over a thousand feet above sea level. Literally closer to the sun, the plants get a higher dose of solar radiation. The growing season is hot and 365 days long.

But Plena’s plants don’t grow exclusively outdoors. Like Organigram and Rosenthal in his consulting capacity, Plena’s seed-to-harvest process has been carefully thought out.

Mothers and clones start their life cycle in a customized-for-cannabis, state-of-the-art greenhouse. After repotting, plants move to standard greenhouses, continuing their vegetative phase before moving outside for the flowering phase.

“There are merits to both indoors and outdoors,” said Zwicky. “You always need a bit of a blend.”

Controlled lighting in the greenhouses prevents flowering, keeping the plants in the vegetative phase longer so that they gain mass, Zwicky said. But most importantly for Plena, greenhouse cultivation allows for consistency across the plants and ensures there is a crop ready to plant once a field has been turned over.

That consistency is key, as medicinal marijuana has to be grown to standards that put an ‘organic’ label to shame, Zwicky said. Instead of pesticides, which would become concentrated during the distilling phase, Plena releases sterilized predator bugs and uses organic horse manure.

In addition to nature, Plena is also embracing Big Data—weather stations gather endless information; crops are analyzed and compared. Combined, the data will inform when different varietals should be planted in order to thrive.

Still, much of that thriving does depend on nature. Outdoor stressors such as solar radiation can prompt production of cannabinoids, allowing for smaller plants with higher levels, Zwicky said.

It is harder to do an outdoor grow without a hybridized system, said Zwicky. But it is possible. If only in South America.

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Celia Gorman
Celia Gorman
Celia Gorman is a science journalist and video editor based out of New York. She holds a master's in digital journalism from the CUNY Graduate School of Journalism and previously worked as an Associate Editor at tech magazine IEEE Spectrum, where she developed and ran an award-winning video section.
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