Canada is, without question, one of the most important cannabis markets on the planet. Its recreational marijuana market opens up nationwide in October, and the biggest marijuana stocks in the world are all based in Canada. But some investors might be overlooking another even more important cannabis market right under their noses -- the U.S.

This year, the U.S. is expected to generate more than 85% of total global marijuana sales. While that percentage will likely decrease as the Canadian recreational cannabis market and medical cannabis markets in Europe grow, the U.S. still is probably going to make up three-quarters of total global marijuana sales well into the next decade.

Marijuana remains illegal at the federal level in the U.S., but that hasn't stopped companies from making headway in the states that have legalized either medical or recreational marijuana. Most of these companies are very small, but not all of them. 

Three marijuana stocks that target the U.S. cannabis market that claim the biggest market caps are Scotts Miracle-Gro (SMG 2.25%), MedMen Enterprises (MMNFF), and MariMed (MRMD 0.73%). Here's what you need to know about these three U.S.-based marijuana stocks.

Marijuana leaves surrounding a rustic U.S. flag

Image source: Getty Images.

1. Scotts Miracle-Gro

Yes, Scotts Miracle-Gro makes over 90% of its revenue from consumer lawn and garden products that have nothing to do with marijuana. However, Scotts' Hawthorne Gardening subsidiary also is the top provider of hydroponics solutions to cannabis growers and is counting on the marijuana market to drive sales much higher in the future. With a market cap of $4.4 billion, Scotts Miracle-Gro easily ranks as the largest marijuana stock targeting the U.S.

Scotts makes the lion's share of its marijuana-related revenue in California. That's not surprising, considering the state is currently the largest marijuana market in the U.S. -- and in the world. The company's Hawthorne subsidiary has underperformed in 2018, though, as a result of a problematic launch of the recreational marijuana market in California.

Jim Hagedorn, Scotts Miracle-Gro's CEO, thinks that the picture is beginning to look better in California. He said on the company's Q2 conference call that product shortages have spurred more cannabis cultivation, which translates to higher sales for Hawthorne. The state and counties also appear to be resolving issues that held back the recreational marijuana market in the first half of the year.

Scotts should benefit from even greater growth in the future as marijuana markets expand in more states. Thirty states have already legalized medical marijuana, and nine states plus the District of Columbia allow the legal use of recreational marijuana. Several states with large populations -- and potentially large marijuana markets -- could also be on their way to legalizing recreational marijuana.

2. MedMen Enterprises

MedMen Enterprises' market cap of around $2 billion makes it a distant second to Scotts Miracle-Gro. However, unlike Scotts, the company is a pure-play marijuana stock. 

When it comes to cannabis retailers, MedMen stands head and shoulders above the pack. The company operates 19 cannabis retail locations in four states. MedMen's biggest presence is in California, where it runs eight cannabis stores.

Those California stores actually beat Apple and Tiffany in the key retail metric of sales per square foot. MedMen's success appears to be largely driven by location. The company's stores are in ideal spots to maximize sales.

But MedMen is busy trying to replicate its model outside of California, as well. The company already operates stores in Nevada and New York and plans to expand into Florida and Massachusetts. MedMen also partnered with Cronos Group to launch retail cannabis stores in Canada.

3. MariMed

MariMed takes the No. 3 spot among U.S. marijuana stocks with a market cap of nearly $600 million. The company hasn't been this big for too long, though. MariMed ranked as the best-performing marijuana stock of the first half of 2018 and has racked up a year-to-date gain of more than 340%.

The company has its fingers in several aspects of the U.S. marijuana industry. Its core business so far has been providing professional management services to marijuana growers. MariMed helps customers obtain state licenses and also develops and operates cannabis production facilities and leases for those facilities to its customers.

MariMed doesn't work just behind the scenes, though. The company markets several of its own brands of cannabis products, including cannabis concentrates, edibles, extracts, flower, and vape pens.

For now, MariMed focuses on five states -- Delaware, Illinois, Nevada, Maryland, and Massachusetts. However, the company plans to move into Florida, Michigan, Ohio, New Jersey, and Pennsylvania in the near future. Two of those states -- Florida and Michigan -- are expected to have cannabis markets topping $1 billion annually by 2022

Is bigger necessarily better?

There are many other marijuana stocks targeting the U.S. market that are smaller than Scotts Miracle-Gro, MedMen, and MariMed. Do these three companies' market caps make them better picks for investors? Not necessarily.

Both MedMen and MariMed, for example, remain unprofitable. There's no guarantee that their investments in expanding will pay off. And while Scotts Miracle-Gro is profitable, it won't benefit as much from growth in the U.S. cannabis market as pure-play stocks will.

However, I like Scotts Miracle-Gro over the long run. Because of its consumer lawn and garden business, the stock is a relatively safe way to invest in the marijuana boom. I'm also keeping a close eye on MedMen and MariMed. If the U.S. market grows like many expect it will, these stocks could be big winners, as well.