Your investing philosophy doesn't have to ruthlessly focus on growth in order for your portfolio to benefit from businesses on a promising trajectory. Whether you're content owning income stocks or prefer to go bargain hunting, stuffing a growth stock or three into your mix of holdings can make all the difference when it comes to long-term performance. You just have to know where to look.

With that in mind, we asked three contributors at The Motley Fool for growth stocks they're watching for reasons that might not be so obvious from headlines and press releases alone. Here's why they chose Antero Midstream (NYSE:AM), Diamondback Energy (NASDAQ:FANG), and lululemon athletica (NASDAQ:LULU).

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This midstream thinks it found liquid gold

Maxx Chatsko (Antero Midstream): This business officially formed in mid-March when two master limited partnerships (MLPs) combined into a single corporation. Unfortunately, that means investors have to wade through complicated pro forma financial comparisons and carefully pore over various adjusted results until the second quarter of 2020. While that can be annoying and might make it easier to focus your attention elsewhere, the extra squinting and head tilting could be well worth it.

Antero Midstream handles the midstream logistics of Antero Resources, which is one of the largest natural gas producers in Appalachia. The region is home to 36% of the nation's total natural gas supply, and the industry expects the region to increase production by 7 billion cubic feet per day by 2023 -- enough to grow America's output 10%. That figures to provide a healthy tailwind for the fee-based business.

In the first quarter of 2019, Antero Midstream grew natural-gas gathering volume 40% and compression volume 60% versus the prior year. That should continue to increase as new long-haul pipelines -- heading toward Gulf Coast export terminals and gas-fired power plants in the Southeast -- open their taps. Freshwater delivery volumes shrank by 31%, but that was driven by an expected decrease in completion activities for new wells at Antero Resources. 

Perhaps the most important opportunity for the business and investors resides in natural gas liquids (NGLs). Unlike natural gas pulled up in the Permian Basin, Appalachian gas is rich in NGLs, which are increasingly being used in petrochemical manufacturing. That provides an important backstop against volatility in the natural gas markets. Antero Midstream is just beginning to enjoy the benefits of a 50/50 joint venture focused on NGLs, which just doubled its fractionator capacity (read: equipment needed to separate NGLs) to 40,000 barrels per day and could soon add another 27,000.

Considering the ample growth opportunities on the horizon, including one that insulates the business from persistent volatility in natural gas markets, Antero Midstream is a growth stock to watch. That's especially true given shares trade at just 11 times future earnings, a PEG ratio of 0.29, and sport an annual dividend yield of 9.9%. 

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A high-octane oil stock

Matt DiLallo (Diamondback Energy): Little-known oil stock Diamondback Energy has delivered prodigious growth since its IPO in late 2012. Thanks to its voracious appetite for mergers and acquisitions, the oil driller's output has risen by a jaw-dropping 785% on a per-share basis over that time frame. And its underlying earnings per share have increased by an even more impressive 850% despite a 37% decline in oil prices. That high-octane earnings growth has helped drive Diamondback Energy's stock up nearly 500% over that period, which has crushed the market's more than 130% total return.

Thanks to the prime position it built up in the low-cost Permian Basin, Diamondback Energy has plenty of fuel to continue growing. The oil producer currently expects to increase its output by another 30% this year. Meanwhile, it has enough high-return drilling locations to grow at a fast pace for the next several years.

The company's resource base is so good that it's on track to produce enough cash flow at $55 oil next year to fully fund a high-octane growth program while generating a gaudy $750 million in excess cash. It intends on using that money to pay its rapidly growing dividend and buy back its attractively priced stock.

Those dual fuels of fast-paced production growth and increasing cash returns to shareholders should enable Diamondback Energy to continue generating market-crushing total returns. So, while most investors are still avoiding oil stocks due to the continued volatility in that market, those who dig a little deeper can see that Diamondback Energy has a proven ability to prosper despite all the turbulence.

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Take a deep breath

Demitri Kalogeropoulos (lululemon athletica): Its shares have more than doubled in the past three years, which means most of Wall Street is well aware of Lululemon's bright growth outlook. But I think investors still might not fully appreciate this retailer's potential.

Sales in the most recent quarter blew past management's targets, with soaring digital orders and robust customer traffic driving a 27% spike, versus the 20% forecast. It easily navigated some significant competitive challenges, including a new threat from Nike, to continue soaking up market share in its core yoga niche while pushing into new areas like outerwear and menswear.

The finances are looking even better thanks to the combination of operating leverage and a continued shift toward online selling, all supported by a packed pipeline of innovative product releases. Together, these trends generated an almost 40% spike in adjusted EPS over the holiday season.

Lululemon might post similarly impressive numbers when it announces first-quarter results in mid-June. Yet even if growth comes in a little light to start the year, the chain appears well positioned to ride its increasing brand strength into new apparel niches and new geographies over the next few years. After passing its $4 billion annual sales goal in 2020, this wider business could deliver a far larger revenue base by the start of the next decade.