Small-cap stocks, or ones with a market capitalization between $300 million and $2 billion, undeniably carry greater risk than mid- and large-cap stocks given their smaller size of operations -- often in the early stages of a business life cycle -- and the restraints that come along with it. Yet small-cap companies also usually grow sales at a fast clip since they start from a small base, and they can generate stupendous returns for investors in the long run if they get their business formula right.

With that in mind, we asked three of our Motley Fool contributors to name one small-cap stock each with solid growth potential. Here's why they chose agribusiness Limoneira (LMNR 0.62%), renewable-energy play TPI Composites (TPIC 13.25%), and biotechnology company Geron (GERN -1.05%).

This stock isn't for sourpusses

Rich Duprey (Limoneira): Third-quarter earnings for citrus grower Limoneira got everyone's lips puckered after sales came in lower than expected and management lowered full-year earnings guidance. Shares that traded north of $33 a stub before the report tumbled as low as $18 before all the juice was squeezed out of them.

Fourth-quarter results were disappointing as expected, but since then, the stock has risen over 30% from its lows, and a good argument can be made that this small-cap stock still has some big potential ahead of it.

A rising arrow over a stack of coins representing income growth.

Image source: Getty Images.

Limoneira has been a leading producer of lemons, avocados, oranges, and specialty citrus fruits since 1893. From the start, it was buying land and water rights and today owns some 14,500 acres, mostly in California but also in Arizona and Chile. Some 5,000 acres are currently planted with lemons, 1,600 have oranges, and 900 have avocados. About 1,500 acres are not producing fruit but are expected to become full bearing over the next four years.

Management is looking for 2019 to be a good year and offered guidance for operating income to hit between $20 million and $23 million, more than double the $9.5 million realized last year. My colleague Asit Sharma notes earnings per share is likely to be volatile because of new accounting rules that impact how it records the sale of its avocado grower Limoneira Calavo, but that's separate from the company's operations.

Limoneira trades at 20 times next year's earnings estimates, which analysts forecast will grow 49%, with long-term annual growth pegged at 15% per year. When life hands you lemons, make lemonade -- and from Limoneira's lowered price point, investors just might want to open a lemonade stand.

Check out the latest earnings call transcripts for TPI Composites, Geron, and other companies we cover.

This wind-energy company wants to double its sales

Neha Chamaria (TPI Composites): When speaking of renewable energy, you'll often find conversations revolve around companies that generate clean energy. Companies that build equipment and components to help utilities generate cleaner power don't get as much attention, but they're just as well poised, if not more so, to benefit from the clean-energy trend. TPI Composites is one such company with a strong foothold in the wind-energy market.

TPI Composites manufactures composite wind blades and boasts an existing customer base that dominates nearly half of the global onshore wind-energy market. Key customers include General Electric (specifically, GE Wind), Siemens, Vestas, and Nordex. With annual wind capacity expected to grow at a compound annual rate of 8.2% between 2017 and 2027 globally, TPI believes its efforts to expand its footprint across mature and emerging markets should ring in strong growth in the years to come.

In fact, TPI aims to double its wind-blade sales by 2021, driven by its existing multiyear supply agreements with key customers and an ever-growing order book. As of the last quarter, TPI's contract value hit a record high of $6.8 billion, meaning that's the amount of potential revenue the company can generate through 2023 under its existing contracts. I expect the number to only grow bigger with time.

There's another interesting thing about TPI: It also has a transportation division that builds composite, lightweight vehicle structures to reduce their weight -- something more and more automakers are seeking in order to boost fuel economy and performance. Albeit currently small, this business could also open up huge opportunities for TPI.

TPI's market cap has more than doubled to $1 billion in just three years. The growth catalysts are well in place for the trend to continue.

A tiny biotech with large aspirations

George Budwell (Geron): Developing novel drugs is a perilous process, one that has forced numerous companies to flat-out go bankrupt. That's the extreme level of risk these types of companies pose to brave, early-bird investors. On rare occasions, however, pre-revenue biotechs can transform into mid-cap -- and even large-cap -- companies with a top product on the market. Geron could be one of these exceedingly rare birds.

Geron is developing a first-in-class telomerase inhibitor known as imetelstat. After a successful mid-stage trial for patients with lower-risk myelodysplastic syndromes (MDS) last year, the company decided to march forth with a pivotal trial for the drug this year. While imetelstat's upcoming late-stage study could take anywhere from two to three years to complete (the details haven't been released yet), the wait might be worth it for investors.

In short, imetelstat is attempting to break into a massive $1.5 billion drug market. There are other drugs barreling toward this particular space at the moment too, but imetelstat would only need to grab a modest proportion of this high-value indication to propel Geron into mid-cap territory. The biotech would then have a viable path toward evolving into a large-cap entity through additional business-development activities -- albeit way down the line from now.

Like most clinical-stage biotechs, though, Geron is one heck of a risky stock. If imetelstat fails in MDS, the blunt truth is that this developmental-stage company would likely fold in the blink of an eye. Geron doesn't have any other clinical assets, and its financial capacity isn't sufficient to bring in alternative candidates at this stage. Therefore, this small-cap biotech arguably shouldn't find its way into your portfolio unless you are comfortable with enormous levels of risk.