What investor doesn't like growth? If a stock generates enough growth, dividends and valuation become relatively insignificant. Growth is king.

We asked three Motley Fool investors which growth stocks they like for the long term. Here's why they chose Green Plains (NASDAQ:GPRE), Impinj (NASDAQ:PI), and Ligand Pharmaceuticals (NASDAQ:LGND).

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More than ethanol

Maxx Chatsko (Green Plains): The world's second-largest ethanol producer hasn't fared well -- nor has the ethanol industry as a whole -- in 2017, but I think Wall Street is largely missing the point. Green Plains has quietly and quickly transformed itself by diversifying into businesses spanning the agricultural vertical, which has already helped to mitigate a historically weak year for ethanol producers. It will provide awesome growth potential for years to come, too. 

Consider that in the last 14 months management has acquired its way to being the world's largest vinegar producer and the country's fourth-largest cattle feedlot owner. Why? Food-grade ethanol is the starting input for food-grade vinegar, and corn byproducts from ethanol manufacturing feed cattle that can be sold as meat. Oh, and vinegar and meat are higher-margin products than ethanol.

Green Plains' food and ingredients segment provided $30.4 million in operating income in the first nine months of 2017, up 217% from the year-ago period. The ethanol segment lost $25.9 million from operations in the same span. That's not all.

The company's tax-advantaged partnership, Green Plains Partners LP, handles logistics and transportation while providing ample profits. It will also begin operating the company's first ethanol export terminals coming on line in November 2017 and the first quarter of 2018. With American ethanol exports reaching record volumes this year, it promises to be the next high-growth business for the company. Regardless of how you feel about corn-based ethanol, Green Plains offers so much more than that -- including above-average long-term growth prospects.

A long-term growth story

Tim Green (Impinj): Shares of Impinj, a provider of radio-frequency identification solutions, have taken a beating over the past few months. Since peaking in June, the stock is down more than 55%. The culprit? A dramatic growth slowdown brought on by delays from customers in the retail industry. Revenue grew by just 5% year over year during the third quarter, and the company guided for a revenue decline in the final quarter of the year.

With revenue moving in the wrong direction, Impinj isn't looking much like a growth stock anymore. But the long-term opportunity for Impinj's object-tracking technology hasn't disappeared. The retail industry alone is an enormous opportunity, with RFID chips making it possible to track inventory in real time and reduce theft. Other industries, like manufacturing and logistics, could also benefit from the technology.

Even with the stock down so much, it's still not cheap. With a market capitalization of about $550 million, Impinj trades for over four times trailing-12-month sales. Growth is going to have to return in a big way for the stock to recover. That probably won't happen in the near term. But if your time horizon is measured in years, and if you're willing to stomach some bad results over the next few quarters, Impinj could be the growth stock for you.

A small biotech that looks like a big one

Keith Speights (Ligand Pharmaceuticals): If you took a look at Ligand Pharmaceuticals' drug pipeline but knew nothing else about the company, you'd probably think it ranked among the largest pharmaceutical companies on the market. Ligand's pipeline includes five late-stage programs, 22 mid-stage programs, and 25 early-stage programs. In addition, the company awaits regulatory approvals for two other drugs. And yet Ligand's market cap is less than $3 billion. 

How can a relatively small company have such an enormous clinical portfolio? Ligand's strategy is to partner with other drugmakers that can benefit from its technology platforms that help make their drugs work better. The company has over 90 partners and licensees, ranging from small clinical-stage biotechs to the biggest biopharmaceutical organizations on the planet. 

Ligand's revenue has more than doubled over the last five years. The company is also profitable. But the journey is just getting started.

Wall Street analysts project that Ligand will increase its earnings by nearly 32% annually over the next five years. I think Ligand's longer-term future should be even brighter. Remember -- the company has over nine times as many early- and mid-stage candidates that use its technology as it does late-stage candidates. It takes time for drugs to win approval then ramp up to peak sales. In my view, Ligand should be a big winner over the long run.

Keith Speights has no position in any of the stocks mentioned. Maxx Chatsko has no position in any of the stocks mentioned. Timothy Green has no position in any of the stocks mentioned. The Motley Fool recommends Impinj. The Motley Fool has a disclosure policy.