Apple (NASDAQ:AAPL) is a solid investment to hold in your portfolio, as the top tech stock's a safe buy and it'll also pay a dividend. But the days of Apple being a high-growth stock are long gone. In its most recent fiscal year, the tech giant saw its sales decline from the prior year. While that doesn't mean that it's run out of ways to grow, for growth investors there may be a better place to invest -- pot stocks.

Pot stocks don't come without risks, but they do come with significant growth potential. Below are three promising cannabis investments that are generating incredible growth numbers and will likely continue to do so as the industry continues to expand.

1. Curaleaf

Curaleaf Holdings (OTC:CURLF) is a multistate cannabis operator with 57 dispensaries and a presence in 18 states. The company's showing no signs of slowing down, either, as it's just weeks away from closing on its acquisition of fellow cannabis producer Grassroots. Once this is complete, Curaleaf's presence will grow to 23 states and it will have 88 dispensaries that are up and running.

Cannabis greenhouse.

Image source: Getty Images.

The Massachusetts-based pot producer's already recording tremendous revenue growth as it is. Curaleaf released its amended first-quarter results on May 20, posting sales of $96.5 million that were nearly triple the $35.3 million that it generated in the prior-year period. Q1's numbers were also up 28% from the fourth quarter, where it reported $75.5 million in revenue.

Curaleaf's been a growth machine, and even if COVID-19 slows it down this year, it's a solid growth stock to hang on to for the long term. The one knock on the stock is that it's struggled to stay out of the red, reporting a net loss in each of its last four quarterly results. But that's been par for the course for many pot stocks during what are still the industry's early growth stages.

2. Aphria

Aphria (NASDAQ:APHA) is one pot stock that's done pretty well when it comes to profitability. On April 14, Aphria released its third-quarter results, marking the fourth period in a row during which the company's adjusted EBITDA was positive. Even net income, without any adjustments, has been positive in three of the past four quarters. 

What's especially impressive is that Aphria is staying profitable while growing its business. In Q3, its revenue of 144.4 million Canadian dollars was nearly double the CA$73.6 million of the prior-year period. It was also a 20% improvement from the second quarter, when its sales were CA$120.6 million.

A big part of the Ontario-based pot producer's growth has come through its subsidiary, CC Pharma, which is based in Germany and sells products to nearly 13,000 dispensaries. In Q3, CC Pharma contributed CA$86.8 million in revenue, which was the bulk of Aphria's distribution revenue of CA$88.3 million.

There's still a lot of growth left in the Canadian market, with edible products only starting to hit store shelves in December of last year. Aphria plans to launch beverage enhancers and other edible products in the first half of 2021. It's also working on developing premium chocolate, topicals, and soft chews. Outside of Canada, there's even more potential growth that Aphria's in a good position to take advantage of, given its subsidiaries in Israel, Barbados, Colombia, and many other countries.

Aphria's a rare pot stock that's not only consistently profitable, but also growing at a phenomenal rate.

3. Green Thumb Industries

Green Thumb Industries (OTC:GTBIF) is another large multistate cannabis operator. With a bit of a smaller footprint than Curaleaf, Green Thumb has licenses for locations in 12 markets. The pot producer announced on June 25 that it would be opening its 47th retail location in Duncansville, Penn., on June 30.

On May 14, the cannabis producer released its first-quarter 2020 results. Sales were up 268% from the prior-year period and grew 35% from the fourth quarter. This was the first period that included sales from its home state of Illinois, where the recreational market launched on Jan. 1. And the company's still continuing to expand its manufacturing and cultivation capabilities in many states, including Illinois, New Jersey, Ohio, and Pennsylvania.

One way Green Thumb stands out from many of its peers is that its operations were cash flow positive in Q1. Rather than burning through cash like many cannabis companies do, Green Thumb posted cash from operating activities of $27 million -- more than enough to fund its property and equipment purchases of $13.2 million. The company's operations have been cash flow positive in two of its last three quarters. That's something that neither Aphria nor Curaleaf can say.

Generating positive cash flow is crucial for a growth stock, especially during the COVID-19 pandemic when many companies are struggling. It can help Green Thumb fund its own growth and minimize the need to issue shares and dilute existing shareholders.

Which is the best buy today?

If you're looking for a high-growth stock, any one of the three pot stocks listed here are great options. But let's also take a look at how they've all done this year, compared to both Apple and the S&P 500:

AAPL Chart

AAPL data by YCharts

Apple's outpaced all the stocks on this list, but over the long term that may not continue to be the case, especially as cannabis legalization progresses in the U.S. and more growth opportunities open up.

The stock I'd go with today is Curaleaf, due to its impressive sales growth and market presence, especially after the Grassroots acquisition. However, all three pot stocks could make for solid growth stocks to buy and hold.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.