Finding quality investments in the cannabis industry can be challenging, simply because it hasn't been around long enough to fully mature. And if you're looking for stocks to buy for the longest of holding periods, the industry's performance over the last few years could be positively frightening. But have no fear, there's (at least) a couple of marijuana businesses that probably won't disappoint the future-you when it comes to their returns. 

Both of the companies I'll discuss today stand to benefit immensely from an increasing level of demand for cannabis products, but neither are reliant on legalization to continue their flourishing. So if you're more interested in a pair of strong investments regardless of how they make money, you're in the right place.

A cannabis worker weighs marijuana flowers while standing behind the counter at a dispensary.

Image source: Getty Images.

1. GrowGeneration

GrowGeneration (NASDAQ:GRWG) is a great stock to hold for decades because it makes the equipment that cannabis operators need to grow their crops. Specifically, GrowGeneration sells hydroponics equipment, grow lights, and plant nutrients, all of which are key inputs for the high-yield indoor cultivation operations that many marijuana companies use. That means as the marijuana industry grows in the U.S., this business will be selling the proverbial shovels that its customers need to participate in the ongoing green and leafy gold rush. 

The anchor of GrowGeneration's operations is its retail depots, which are scattered throughout the U.S. in the cannabis markets that are projected to be the largest centers of cultivation, like Pennsylvania, New York, California, and others. That means it's front-running federal cannabis legalization while also capturing revenue from the state-level markets that are ahead of the game. As a result, the company is perfectly positioned to benefit from both the status quo and the anticipated changes to it. 

Retailing hydroponics gear is a narrow-margin line of work, but GrowGeneration is making the most of it, as its income is increasing at a snappy pace. Per its Q3 update, quarterly revenue rose by 110.9% year over year, and earnings rose by 20.6%. And there's reason to believe that its customers will keep coming back for more: 60% of its revenue is from sales of consumables, and if its customers want to keep growing cannabis, they'll need to keep buying. 

Moving forward, GrowGeneration increase its offerings of private label products for which it is the exclusive distributor. Of course, that'll just tide shareholders over until the real prize of surging demand from legalization occurs, whenever that may be.

2. Innovative Industrial Properties

Innovative Industrial Properties (NYSE:IIPR) has a well-justified reputation for being the marijuana industry's landlord, and it's no surprise why. With its 7.5 million square feet of rentable floor space dedicated solely to cannabis cultivation, IIP is the go-to stock for investors seeking a marijuana-centric real estate investment trust (REIT).

Like GrowGeneration, Innovative Industrial is positioned in the nation's hottest marijuana-growing regions like New York, California, and Pennsylvania. Its tenants are obliged to take long-term leases that on average span 16.7 years, so its recurring revenue is relatively insulated from disruption. And as long as IIP has incoming rent payments, it can afford to buy new cultivation facilities, which it then leases back to the prior owner to create a new income stream. 

Because the company purchases real estate in exchange for a rental income stream, it's a popular partner for cannabis companies that own property but need to raise cash for large growth initiatives. That makes it an obvious benefactor from the marijuana industry's continued expansion over time, and investors reap the rewards too.

In the third quarter of this year, its revenue rocketed upward by 57%. At the same time, its dividend, which has a trailing yield of 1.98%, is now 28% higher than it was a year prior. Since the initiation of the dividend in 2017 at $0.15 per share, it has grown to reach $1.50, a tidy increase of 900%.

More dividend hikes are likely on the way. Over the next couple of decades, holding IIP stock will likely be immensely profitable for people who invest today, and that makes it my favorite cannabis stock for the long haul.

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.