If you aren't investing in growth stocks, you're missing out on significant gains. In the past decade, the Morningstar Growth Index has returned 16% per year, versus only 10% for the Morningstar Value Index. The rise of growth stocks has been so remarkable that billionaire hedge fund manager David Einhorn has openly questioned whether value investing was dead.

However, there's no such thing as a free lunch in investing. The trade-off is that growth investing is riskier, since growth companies tend to have richer valuations and higher levels of volatility. With that in mind, we asked three Motley Fool specialists to cut through the clutter and identify three great growth stocks to buy right now. Find out why iRobot (IRBT 0.33%)MercadoLibre (MELI 0.95%), and American Homes 4 Rent (AMH 0.89%) made the cut.

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Capitalizing on big trends

John Bromels (iRobot): Robotic vacuum manufacturer iRobot is sitting in a sweet spot for growth investors. It hasn't gotten too big yet; in fact, its market cap of about $3.4 billion is at the low end of "mid-cap" status. But it's already growing by leaps and bounds, as that market cap has doubled over the past two years. And thanks to some big trends it's riding, iRobot seems likely to continue growing. 

The first trend working in iRobot's favor is automation. As technology advances, machines are able to do more of our work for us. And people are becoming more comfortable with, and accustomed to, having robots do the work. But the market for such devices is still pretty small: These things aren't cheap. However, the addressable market is huge, and iRobot's Roomba, although the top dog in the robotic vacuum space, is barely scratching the surface of the overall high-end vacuum market. Add in the market for the company's recently announced robotic lawn mower, and you can see that this is a company with big growth potential.

iRobot is capitalizing on that potential through another trend: integrated smart home systems. Some of iRobot's recent Roomba models can be activated simply by telling your Amazon Echo smart speaker to start the vacuuming. As these systems enter more and more homes, people are going to look for ways to put them to good use. And what better use than sending robots to do the chores? 

The market is catching on to iRobot's potential. Shares have jumped 44.5% so far this year. But there's still time to buy into this top growth stock before the ship has sailed -- or rather, before the Roomba has started vacuuming. 

Robotic vacuum cleaner on a hardwood floor.

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MercadoLibre has a secret growth driver

Jamal Carnette, CFA (MercadoLibre): Shares of MercadoLibre are on a tear this year, up nearly 75% as of this writing on the back of a positive fourth quarter. At first glance, it may appear the company's growth has slowed, as the top line increased 18% for the quarter. But that was due to a strengthening dollar; on an FX-neutral basis, the company grew revenue 62%.

However, the real key was where MercadoLibre's growth was coming from. Last year was the first time non-marketplace revenue eclipsed marketplace revenue, as the former increased 54%, dollar adjusted. A big reason for this growth is its MercadoPago fintech product, which resembles PayPal. This quarter was the first time MercadoPago had more payments from outside its e-commerce site than on it, which portends continued growth for the product. This higher-margin, highly scalable business has the potential to drive MercadoLibre's next phase of growth.

Demographics will continue to provide tailwinds for MercadoLibre. Latin America will continue to grow from emerging markets into developed ones as households increase their disposable income and internet penetration grows. Being in the front row of e-commerce and payments is a reason for long-term investors to own shares of MercadoLibre.

Home with rental sign in the front yard.

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Foundation for the future

Rich Duprey (American Homes 4 Rent): Although it has recovered from the bottom it hit in 2016, homeownership rates in the U.S. remain at historic lows, and that's pushing demand for rental housing higher. American Homes 4 Rent is a real estate investment trust that could benefit from that trend, as it's focused on the single-family home rental industry.

Shares of the REIT have climbed 22% since their December lows, as it's been able to lease a greater number of homes and has enjoyed high rental rates, which helped push fourth-quarter revenues up 11% year over year, along with a similar increase in core net operating income.

Housing market trends seem to favor American Homes' continued rise. Household creation has outstripped supply for years, a byproduct of the financial recession of the last decade, and Fannie Mae says inventory of existing single-family homes for sale has tumbled over 30% nationwide since 2011, while the sale price on homes soared 57%. With more people looking for homes but either being unable to find them or being priced out of the market, the demand for rental housing has risen.

Analysts see American Homes 4 Rent enjoying substantial earnings growth in the years ahead, as it turns from generating losses in 2017 to making profits in 2018. They're looking for earnings per share to triple this year and then grow in excess of 60% annually for the next five years.

That's not to say American Homes' stock is cheap, trading at nearly 300 times trailing earnings, but stocks of companies that cross over from loss-making to profit-generating typically have skewed multiples. Still, with housing trends at its back, this home rental REIT could be a growth stock you'd want to buy right now.