The legal marijuana industry is big business. According to investment firm Cowen & Co., the cannabis industry is expected to generate $75 billion in sales by 2030. That's up from a previous forecast of $50 billion by 2026. That's a lot of dollars, and presumably some companies have to come out a winner.

But it's what happened in 2018 that's really caught the attention of investors. With Canada ending nine decades of recreational marijuana prohibition, the idea of pot being taboo was thrown out the window. Instead, the legal weed industry is now viewed as a legitimate business model. In short, it might be the investment opportunity of a generation, if it lives up to sales projections and institutional hype.

Cannabis buds next to an index card with the worth yes on it, lying atop dozens of miniature Canadian flags.

Image source: Getty Images.

Although the industry is still in its infancy, Canada's legalization is expected to result in $5 billion or more in added annual sales by the early part of the next decade. Once growers have had time to complete their capacity expansion projects and receive all required cultivation licenses and sales permits, the industry should blossom. That means it could be full of opportunity for investors.

If you're looking to take part in the green rush, the following three Canadian pot stocks could be the best way to put your money to work.

OrganiGram Holdings

There's arguably no marijuana stock in Canada that offers better bang for your buck than OrganiGram Holdings (NASDAQ:OGI). As you'll soon see, all three of these best Canadian buys are cannabis growers, but they all offer differentiation in unique ways.

The first thing you'll probably notice about OrganiGram is the company's location in New Brunswick (NB). Whereas most growers are located in Ontario, Quebec, or British Columbia, OrganiGram is the only grower projected to be in the top 10 of aggregate production at peak capacity that's based in an Atlantic province. That gives it a competitive advantage in these eastern provinces and territories, and is a big reason it has potentially remained under the radar, according to OrganiGram CEO Greg Engel.

OrganiGram also operates just a single grow location in Moncton, NB. The advantage of this is that it can centralize its supply chain from one location, rather than from two or more locations throughout the province or Canada. Presumably, this should be a means to lower overall production costs.

An indoor commercial cannabis-growing greenhouse.

Image source: Getty Images.

There's also OrganiGram's three-tiered growing system at Moncton. Rather than growing cannabis plants and "wasting space," OrganiGram's indoor grow farms feature three levels of marijuana plants, which maximizes the usage of its 490,000 square feet of production capacity. When the four-phase expansion of Moncton is completed in October 2019, and assuming OrganiGram also has licensing and permitting in place, it'll have the capacity to yield 113,000 kilograms per year. There are other growers with more than double this capacity that won't produce the same amount of cannabis annually as OrganiGram.

Tack on an exceptionally low forward price-to-earnings ratio of 17 to go along with the company's expected sales growth of 891% in fiscal 2019 and 87% in fiscal 2020, and you have what looks to be an incredible bargain.

CannTrust Holdings

Check out the latest CannTrust Holdings earnings call transcript.

Another grower with a very compelling valuation is Ontario-based CannTrust Holdings (NYSE:CTST).

CannTrust operates two facilities: the Vaughan facility and the Niagara perpetual harvest facility. The Vaughan facility is more of an afterthought, with 60,000 square feet of production capacity. Meanwhile, the Niagara facility could, at its peak, reach beyond 1 million square feet of production.

Have things been perfect up to this point for CannTrust? Well, no. In June, the company opened up 450,000 square feet of its Niagara facility, which is the second phase of its proposed expansion. However, the 600,000-square-foot third phase has been held up by permitting in the town of Pelham. Originally expected to be completed around the end of calendar year 2018, there's a bit of uncertainty as to when this phase 3 expansion will receive all necessary permits. When the company is able to receive its proper permits and completes construction, it should be on track for 100,000 kilograms or more in peak annual yield. This should slot CannTrust into the top 10 in terms of aggregate annual output in Canada. 

An indoor hydroponic cannabis grow farm.

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What's particularly unique about CannTrust -- and why its capacity expansion delay in Pelham isn't a backbreaker -- is the company's focus on hydroponic growth. Hydroponics involves growing plants in a nutrient-rich water solvent as opposed to soil. With abundant sources of low-cost water and electricity nearby, to go along with moving containerized benches that lead to a perpetual harvest rather than lumpy production, CannTrust's per-gram production costs should easily be in the bottom third of the industry.

In the early going, CannTrust has also leaned on cannabis oils as a substantial percentage of total revenue, more so than any other pot stock. Oils are a higher-margin consumption option compared with traditional dried cannabis flower. At 26 times forward earnings, CannTrust doesn't appear to be as inexpensive as OrganiGram, but its triple-digit forecasted sales growth in each of the next two years could easily make up for that.

HEXO Corp.

Long-term investors should also find success with Quebec (QC)-based HEXO (NYSE:HEXO), which, according to the company's management team, has the ability to produce 108,000 kilograms of cannabis at peak capacity. Once again, that should be enough to proclaim HEXO a top-10 grower by peak annual output.

HEXO already has approximately 310,000 square feet of completed grow space, but it's set to finish a 1 million-square-foot capacity expansion project adjacent to its Gatineau, QC, facility any day now. This roughly 1.3 million square feet, while nowhere near as space efficient as OrganiGram, will help HEXO become a top grower.

A large cannabis buds lying atop a messy pile of hundred dollar bills.

Image source: Getty Images.

What makes HEXO unique is twofold. First, it signed a mammoth supply deal with SQDC -- the Quebec regulatory body that oversees the cannabis industry within the province -- in 2018 that'll see HEXO deliver an aggregate of 200,000 kilograms of pot over a five-year period. The amount deliverable increases with each passing year. The key point here being that a significant portion of HEXO's annual output is already accounted for, which means plenty of predictable cash flow.

The other alluring factor is the company's Aug. 1-announced joint venture with Molson Coors Brewing Co. (NYSE:TAP). Molson Coors, which owns 57.5% of the joint venture, will be working with HEXO to research, develop, and market cannabis-infused beverages, with the launch of the first product expected later this year, assuming Canada's Parliament approves new consumption by this summer. Molson Coors has seen its beer market share erode over the past decade in Canada and is counting on this partnership to reignite its sales in the region.

Also valued at 26 times forward earnings, HEXO appears reasonably inexpensive. If its partnership with Molson Coors works out, and the company's licensing and permitting remains on track, Wall Street foresees HEXO's annual sales growing from less than $4 million in fiscal 2018 to almost $180 million by fiscal 2020. That type of growth is bound to attract investors.