After a tumultuous year in 2018, many marijuana stocks have stormed out of the gate so far this year. You'd have to use all of your fingers and some of your toes to count the number of marijuana stocks that are up 50% or more in 2019.

We asked three Motley Fool contributors to identify which top marijuana stocks they think investors should especially watch in April. Here's why they picked Aphria (NYSE:APHA), HEXO (NYSE:HEXO), and Scotts Miracle-Gro (NYSE:SMG).

Marijuana plants growing in a greenhouse

Image source: Getty Images.

The first peek at Canada's recreational market in 2019

Keith Speights (Aphria): All of the big Canadian marijuana producers have now reported their results from the end of 2018. Those results, of course, included the first partial quarter of sales in the Canadian adult-use recreational marijuana market. But for investors anxious for a hint at what this market could look like in 2019, all eyes should be on Aphria.

In January, Aphria posted soaring sales in its quarter ending Nov. 30, 2018. But those results only included a couple of weeks of sales in the adult-use recreational market. Aphria's news was also overshadowed somewhat by the planned departure of longtime CEO Vic Neufeld.

The company is scheduled to announce results from its quarter ending Feb. 28 on Monday, April 15. This should be especially interesting as Aphria will be the first major Canadian marijuana producer to report numbers from the first two months in calendar 2019 for the adult-use recreational market. I expect Aphria to show that it's in a solid third position in this market, behind only Canopy Growth and Aurora Cannabis.

Aphria's stock performance has lagged behind its peers over the last 12 months. So far this year, though, its shares have skyrocketed, beating several of the other big Canadian marijuana stocks. I suspect that Aphria's next quarterly update could provide the fuel needed for another big jump for the stock.

An acquisition makes this marijuana producer especially intriguing 

Todd Campbell (HEXO): If you're not paying attention to small-cap marijuana grower HEXO yet, you ought to be. The company recently unveiled guidance for future revenue that suggests sales will climb substantially in the coming year, potentially rewarding investors with handsome returns in the process.

A small player in the emerging marijuana industry, HEXO only sold marijuana in three Canadian provinces last quarter. It recently acquired Newstrike, however, giving it the opportunity to market products in eight of the country's 10 provinces. The larger addressable market is particularly good news because HEXO's already proven it can compete. Its market share is about 30% in Quebec, Canada's second most populated province, and as a result, its sales were 16.2 million Canadian dollars in the fourth quarter.

Growing demand in Quebec and the opportunity to market marijuana elsewhere has management guiding for fiscal 2020 sales of CA$400 million. Given its existing annualized run rate is just CA$64 million, HEXO's future could prove to be profit-friendly for investors. 

The fertilizer company that has embraced weed

Chuck Saletta (Scotts Miracle-Gro): While it may have once been best known for being the official lawn care company of Major League Baseball, Scotts Miracle-Gro has made several recent big bets on the marijuana industry. The Hawthorne subsidiary it owns is all about hydroponics -- growing systems frequently used to produce marijuana plants. Recent acquisitions to support that business leveraged its balance sheet and helped send its stock tumbling last year.

Still, despite the short-term pain from those investments, there are signs that they may be beginning to produce results. In its January earnings announcement, Scotts Miracle-Gro indicated that its Hawthorne business increased revenue by better than 80% on a year-over-year basis. That revenue growth provides reason to believe that Scotts may actually get sufficient value from the business to justify those investments.

Still, the company lost money on the quarter, a testament to the fact that its business is still heavily tied to the seasonal lawn care business. Those losses, when combined with the fact that Scotts Miracle-Gro's debt has ballooned, as it has invested heavily in the marijuana business, should give investors pause before jumping in with both feet.

The growth it is now seeing in its marijuana-focused business certainly makes Scotts Miracle-Gro worth watching. While watching it, investors should keep an eye out for how well it handles the increased debt load with the still-seasonal nature of its operations. Excitement over its growth has helped its shares recover, but a future debt-related stumble may provide the opportunity to buy in at a better value for the total business it operates.