When you're looking for engines of growth to fuel your portfolio, marijuana stocks just might be up your alley. With the cannabis industry still in its infancy in the U.S., there are plenty of upstarts that are building the foundations of future prosperity as they become established in their markets. And at least a few of those competitors have the enduring appeal that makes for a great investment. 

Both of the cannabis companies I'll discuss today are small, and in the early stages of their lifecycle. In fact, their sales are increasing so quickly that it's possible that it'll cause these stocks to double over the next two years. Let's dive in and see how. 

Farmer standing in a field of cannabis gives a thumbs up while holding a tablet.

Image source: Getty Images.

1. MariMed

MariMed (MRMD -2.35%) is an up-and-coming pure-play medicinal cannabis business that's growing at a white-hot pace while remaining profitable. Between its sales at dispensaries and licensing fees from other players looking to sell MariMed's products, its quarterly revenue has grown by more than 846% in the last three years. 

It's realistic that it could double over the next two years because the company expects to make more than double its FY2020 revenue in 2021, potentially reaching $118 million in total, and it's already more than halfway there. Plus, last year it made a record $17.87 million in normalized earnings before interest, taxes, depreciation, and amortization (EBITDA), which it'll also likely double.

Moving forward, its three dispensaries under construction will be a large addition to its footprint of seven, meaning that even more new sales opportunities are just around the corner. As though that weren't enough, management is planning for dispensary capacity expansions and licensing programs that it expects could be worth at least another $120 million per year.

If MariMed nails its goal of $118 million in 2021, then executes its expansion plans successfully in 2022, it'll have doubled its revenue twice in two years, and that makes it quite an exciting stock.

Charts showing MariMed's and Planet 13's revenue and EBITDA since 2019.

MRMD Revenue (Quarterly) data by YCharts

2. Planet 13

Much like MariMed, Planet 13 Holdings (PLNH.F -6.00%) is a small cannabis seller with ambitious expansion plans. At the moment, its biggest asset is its flagship stores located near the Las Vegas Strip, which enables it to capture a stunning 9% of the Nevada market for marijuana on its own. 

In the last three years, the store in Vegas has been an unqualified success, and Planet 13's quarterly revenue has risen by nearly 300%, whereas its total operating expenses as a percentage of revenue have fallen by 26.81%. In other words, new income is flowing in at a faster and faster pace while Planet 13's costs are falling. A small amount of this new income is likely due to the two new stores that it opened in the last year, and more are soon on the way.

Through 2026, the company plans to open more than eight new retail locations, all in lucrative markets like Illinois, which will be a tremendous increase over its current set of three. Before that, its newer locations will start to scale up their operations and see more sales. Even if they can't match the Vegas store's $70.5 million in sales during 2020 right away, they'll still make significant contributions to the top line.

While there hasn't been a full quarter since the new stores opened, the last earnings report did have a teaser for investors that bodes well for Planet 13's future and its chances of doubling. In Q2, quarterly revenue reached $32.84 million, a 205.2% increase year over year. With growth like that, it won't take too long for this stock to get recognized by the market and boom in value.