There may be no better illustration of the power of compound growth than the long-term chart of a growth stock. Investors can likely list off the names of several of the best well-known examples, including Amazon, Apple, and Priceline

That said, there are quite a few great opportunities for open-minded investors looking for growth. They may not be household names or operate flashy businesses, but three growth stocks I'd buy right now are Green Plains (GPRE -0.64%), Scotts Miracle-Gro (SMG 3.45%), and Clean Energy Fuels (CLNE 2.70%).

Successively larger stacks of coins with seedlings on top, symbolizing growth.

Image source: Getty Images.

An under-the-radar growth stock

Green Plains has been hard at work trying to broaden its image as a purely biofuels stock. It shortened its name (removing "Renewable Energy" from the end). It expanded vertically into higher-margin businesses. Nonetheless, Wall Street has stubbornly refused to take notice -- or remained blissfully ignorant. You shouldn't make the same mistake.

The business is stronger and the dividend is higher than at any point in the company's history, but shares have dipped below $20 in recent months. 

GPRE Chart

GPRE data by YCharts.

While political uncertainty is causing fear of regulatory obstacles for ethanol producers (don't bet on any major changes), Green Plains has positioned itself to become more and more insulated from the constant volatility the first-generation biofuel has endured. That makes it an under-the-radar growth stock -- and one that will become more profitable as it grows.

Why? Since October 2016 management has acquired the world's largest food-grade vinegar producer and various cattle feedlot operations. The two newest business focuses are higher-margin than ethanol and require inputs such as food-grade ethanol and corn byproducts that aren't exactly in short supply at Green Plains. Better yet, the new businesses are already pulling weight.

Consider that the food and ingredients segment accounted for just 11% of revenue in the first quarter of 2017, but 55% of total operating income. Moreover, the vinegar and cattle businesses aren't fully integrated into the Green Plains universe yet, which suggests even higher margins are on the horizon.

Throw in a PEG ratio of 0.19 (which is virtually unheard of), a forward price-to-earnings (P/E) ratio of 11, and a dividend yielding 2.5%, and this is quite the buying opportunity for what should be a formidable growth stock. 

Familiar brands under one roof

Scotts Miracle-Gro hasn't had any problems growing in the last five years. While shares have recovered from a brief lack of confidence earlier this year to jump back over $93 per share, they could be headed higher.

SMG Chart

SMG data by YCharts.

The business has been powered through organic growth and opportunistic acquisitions and partnerships. Both mechanisms have inserted highly reputable consumer brands into the company's portfolio including Miracle-Gro, Scotts, Roundup, TomCat, and Bonnie's. New product launches promise to keep organic growth humming along. For instance, the new "Roundup for Lawns" is expected to reach first-year sales of $40 million in 2017 ahead of new formulations next year.

The opportunity in hydroponics has also caught Wall Street's eye, with some even considering Scotts Miracle-Gro the most solid growth stock in the marijuana industry. Although not broken out into its own business segment, hydroponics notched year-over-year revenue gains of 22% during the fiscal second quarter of 2017.

Plus, a big reshuffling of operations should act as a multiplier on existing growth opportunities. Scotts Miracle-Gro will be taking itself out of international markets, having recently agreed to sell its businesses in Europe and Australia. The financial terms aren't overwhelming -- the price tag was just $250 million -- but the deal allows the company to double down on the U.S. market, which is where the most growth potential resides. 

Natural gas fuels, anyone?

Clean Energy Fuels has never really had any problems growing revenue. Instead, the problem was struggling to balance growth investments with profitability. When energy markets turned sour and fleet adoption turned out to be slower than expected, the natural gas transportation fuels leader's stock had only one direction to go: down.

But things may be about to change for good. Really.

CLNE Chart

CLNE data by YCharts.

Management has reined in expenses, paid off debt (which means it should be done with the ridiculous levels of dilution), and even pulled in $155 million from BP in early March. Although it was technically an asset sale, the two signed a long-term supply agreement for renewable natural gas that is processed and sold as transportation fuel under Clean Energy Fuels' Redeem brand. It's among the fastest-growing parts of the business -- and now BP can help to expedite its broader adoption. 

Those efforts appear to be paying off already. In late May, the Los Angeles County Metro awarded Clean Energy Fuels a contract to supply the nation's largest compressed natural gas (CNG) bus fleet -- totaling some 2,200 buses -- with Redeem fuel. If all goes well during a one-year pilot program, then it could result in an additional 38 million gasoline gallon equivalents (GGEs) of annual sales. To put that in perspective, the company sold a total of 58.6 million GGEs of Redeem in 2016 and 329 million GGEs of total natural gas fuels. 

I haven't been the biggest fan of Clean Energy Fuels in recent years, but I have to give credit to the management team for putting the company on what appears to be solid footing for years of growth. Since Mr. Market hasn't fully priced in all of the potential (understandably, given past performance), this is a growth stock I would buy right now.