What are the top three U.S.-based marijuana growers that are publicly traded and have market caps of at least $500 million? If you're having trouble coming up with names of the companies, don't feel bad: There aren't any U.S.-based companies that meet the criteria.

If we substituted Canada for the U.S., though, it wouldn't be very hard to find marijuana growers with relatively sizable market caps. Canopy Growth Corporation (NASDAQOTH: TWMJF), for example, is currently valued at close to $1.7 billion. Aurora Cannabis (NASDAQOTH: ACBFF) has a market cap of more than $900 million. Aphria's (NASDAQOTH: APHQF) market value is more than $800 million.

While these three companies focus primarily on the rapidly expanding Canadian marijuana market, one of them also has its eyes set on Canada's southern neighbor. Here's why Aphria is a Canadian marijuana stock that's also a bet on the U.S. cannabis market.

Getting hotter

Aphria is headquartered in Leamington, Ontario, where the normal temperature in January is nearly 23 degrees Fahrenheit. The company grows its marijuana crops in greenhouses. In fact, Leamington is sometimes referred to as "the greenhouse capital of Canada."

The company expanded a few months ago to a much warmer climate, though. In May, Aphria announced that it had completed a strategic investment in DFMMJ Investment Ltd., a special-purpose private company. That move was important, because DFMMJ also entered into an exclusive management agreement at the same time with Chestnut Hill Tree Farm, located northwest of Gainesville, Fla.

Chestnut Hill is one of only seven licensed dispensaries of medical cannabis in the state of Florida. Aphria, through DFMMJ, will exclusively manage and operate Chestnut Hill, including all cultivation, processing, and dispensing of medical cannabis to patients in Florida. Once new regulations are implemented in the state, it's expected that Chestnut Hill will transfer its cannabis-dispensing license to DFMMJ.

How big of a deal is this for Aphria? Florida represents roughly 14% of the total U.S. medical-marijuana market. ArcView Market Research estimates the Florida market will grow to more than $1.1 billion annually. By comparison, Aphria made less than $17 million in sales in the past 12 months. Florida could literally and figuratively present a hot market for the Canadian company.

Just a start

Florida is just the first of what could be a major expansion by Aphria into the U.S. market. DFMMJ plans to target other "key U.S. states that have approved medical use of marijuana" for expansion. Vic Neufield, Aphria's CEO, stated that the Chestnut Hill deal "is only the beginning for our plans to be a dominant player in the medical-cannabis industry internationally."

Analytics company New Frontier Data, which focuses on the cannabis market, projects that the U.S. medical-marijuana market will grow by a compound annual growth rate of 12% through 2025. If these projections prove accurate, the medical-marijuana market in the U.S. will top $13 billion annually within the next eight years.

While Aphria only talked about the medical-marijuana market with the Chestnut Hill arrangement, the company is no doubt also thinking about the possibility of expanding into the U.S. retail marijuana market. New Frontier Data thinks the legal recreational-marijuana market could reach nearly $11 billion by 2025 -- and that estimate only reflects the states that had legalized the drug as of January 2017.

It's quite possible that the actual market size could be significantly larger. More states could consider legalization of recreational marijuana, particularly New Jersey, which could become the second largest market for recreational marijuana after California if legalization efforts in the Garden State are successful.

Risky bet?

What are Aphria's peers doing with respect to the potentially huge U.S. marijuana market? Canopy Growth has stated that it only wants to do business "in jurisdictions where it is federally legal to do so." With marijuana still illegal at the federal level in the U.S., that means the company will probably focus elsewhere.

Aurora Cannabis entered into a partnership with AJR Builders Group a couple of years ago to build a new marijuana production and processing facility in Washington state. However, the company talks a lot more about its opportunities in Germany and Australia these days than it mentions U.S. expansion plans.

Canopy Growth, and possibly Aurora to a lesser extent, appear to see the U.S. market as too risky of a bet right now. That raises the question about whether Aphria might be too risky of a bet itself. That could well be -- but probably not primarily because of Aphria's U.S. strategy.

Aphria's shares currently trade at nearly 50 times sales, with an enterprise value-to-EBITDA ratio of nearly 207. Those valuation metrics are sky-high. An enormous amount of growth is baked into this stock already. Any hiccups in achieving this growth could send Aphria stock headed south.

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Keith Speights has no position in any of the stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.