If you've been trading marijuana stocks hoping to make a lot of money fast, stop it. Even if you've been really lucky so far, it's time to change your perspective. Shift your focus from the short term to the long term. Why? First of all, you're more likely to generate solid returns. And the reality is that there are several marijuana stocks that have a really good shot at being long-term winners. Three that I think fit the bill are CannaRoyalty (NASDAQOTH:CNNRF), Canopy Growth (NYSE:CGC), and Scotts Miracle-Gro(NYSE:SMG). Here's why these look like great marijuana stocks to buy in October.

1. CannaRoyalty

At first glance, CannaRoyalty might look like yet another Canadian marijuana business. It's based in Ottawa. CannaRoyalty stock is listed on Canada's New Stock Exchange (CNQ). And the company has funded revenue streaming deals with several small Canadian marijuana growers. But CannaRoyalty isn't your typical Canadian marijuana stock.

Although CannaRoyalty remains active in funding deals in Canada, California is where the real action is for the company. Thanks to some strategic acquisitions, CannaRoyalty ranks as the largest distributor of legal cannabis products in the state. As the company states to investors, "Canada is big. California is huge."

That's not just spin. Arcview Market Research and BDS Analytics project that the total Canadian marijuana market will be around $5.5 billion by 2022. California's marijuana market is expected to top $7.7 billion by then. It's no small feat to be the largest distributor in the largest marijuana market in the world.

CEO Marc Lustig recently said that the company is only at the beginning of "a multi-quarter parabolic step change in revenue." My hunch is that he's right. The company's early investments have begun to pay off nicely, providing CannaRoyalty plenty of cash to expand and fuel more growth. I continue to view CannaRoyalty as the best under-the-radar marijuana stock I've seen so far.

2. Canopy Growth

Canopy Growth stands as the top marijuana stock in terms of market cap (although it briefly surrendered its No. 1 spot to Tilray for a few days). I think that Canopy deserves its premier position and is in the best position of any Canadian marijuana grower to thrive over the long run.

The company's relationship with big alcoholic beverage company Constellation Brands is a key reason I think so highly about Canopy's prospects. Constellation bought a 9.9% stake in Canopy last year. But the Corona beer maker's recent $4 billion investment in Canopy totally changed the dynamics in the cannabis industry.

As a result of this massive investment, Canopy now has a huge cash stockpile that it plans to use to rapidly expand. Canopy co-CEO Bruce Linton stated that his company has a list of potential acquisition targets to cement its leadership position in the industry.

I can understand that some investors might be reluctant to buy Canopy with its market cap now approaching $12 billion. However, my view is that the global cannabis market over the long term will easily top $100 billion. I think that Canopy will continue to be a leader in this market, giving the stock plenty of room to run over the next decade.

3. Scotts Miracle-Gro

Many investors are too risk averse to jump into marijuana stocks like CannaRoyalty and Canopy. I think that Scotts Miracle-Gro presents an attractive alternative for these conservative investors who would still like to profit from growth in the cannabis industry.

Scotts makes more than 90% of its total revenue from sales of consumer lawn and garden products. This side of the company's business benefits from longer warm seasons. The National Oceanic and Atmospheric Administration (NOAA) predicts that the climate will continue to warm in the coming years. While these trends could be negative in some ways, they could help Scotts Miracle-Gro's core business.

The company ranks as the largest U.S.-based marijuana business in terms of market cap due to its Hawthorne Gardening subsidiary. Hawthorne ranks as the No. 1 supplier of hydroponics products to the U.S. cannabis industry, with its largest market, not surprisingly, in California. The company's cannabis business should increase considerably as more states legalize medical and recreational marijuana and as the markets mature in states that have already legalized marijuana.

Scotts Miracle-Gro stock is down so far in 2018 due to problems with California's launch of its recreational marijuana market and a late start to spring. I think that buying Scotts in October could set up investors for a nice bounce next year.  

Risks

I like CannaRoyalty, Canopy Growth, and Scotts Miracle-Gro and think their long-term prospects look good. However, I would be remiss in not pointing out several risks for these stocks.

CannaRoyalty and Scotts operate in the U.S. cannabis market, where marijuana remains illegal at the federal level. Although I don't think the feds will crack down on businesses in states that have legalized marijuana, it's still a possibility. Any signs of such a move would likely cause shares of CannaRoyalty and Scotts to tumble.

Many assume that Canada's recreational marijuana market will get off to a strong start in a few weeks. But there's a chance that demand won't be as great as predicted. Weaker-than-expected demand would probably take a bite out of Canopy's market cap.

As I said at the outset, though, it's better to think long term instead of short term. Over the long term, my view is that all three of these marijuana stocks are poised for success.