The once lowly kumara or sweet potato is being reborn as a kind of hip, orange super food.
Gone are the days when the only time Americans encountered the tuber was mashed up and topped with marshmallows alongside a Thanksgiving turkey.
Today, sweet potatoes turn up everywhere, as healthier, nutrient-dense alternatives to French fries at burger joints or colourful side dishes for swanky restaurants. They have more fibre and fewer calories than white potatoes.
And the appeal isn't just among Americans, who are eating twice as many sweet potatoes as they did in 2002. Demand also is surging in Europe.
In the US, the world's biggest exporter, farmers are planting their biggest crop in five decades after their shipments overseas doubled in five years to an all-time high. Nutritionists say consumers who want to eat fewer grains and processed foods are choosing sweet potatoes.
"We've seen various different plants emerge as new superstars," said Kristin Kirkpatrick, manager of wellness nutrition services at Cleveland Clinic Wellness Institute.
"From a diet perspective, people are so interested in really eating much closer to the farm. Sweet potatoes could be clumped in with beets and kale and some of these other things that are coming from the ground and not coming from a plant where people are wearing hairnets."
While Americans still eat far more white potatoes - as French fries or just baked or mashed - demand has slowed. Consumption was 51.6kg per person last year, down from 56.8kg a decade ago, the US Department of Agriculture estimates.
Sweet potatoes are catching on and growers are marketing them as a year-round staple. In 2015, consumers ate 3.4kg, up from 2kg in 2005 and 1.6kg in 2002, USDA data show.
Sweet potatoes, which belong to a different plant family than white potatoes and yams, were already well-established as a root vegetable in Central America and South America by the time explorer Christopher Columbus arrived in the late 1400s.
They were a big part of the US diet almost a century ago, peaking in the 1930s, before falling out of favour over the next six decades. With demand and output now rebounding, the crop is marketed in everything from dog food to vodka.
Wikipedia notes that here: "Kumara is particularly popular as a roasted food or in contemporary cuisine, as kumara chips, often served with sour cream and sweet chili sauce".
The same approach happens in the US.
"They've been phenomenally popular" at DMK Burger Bar in Chicago, where sweet-potato fries served with a lemon-Tabasco aioli have been on the menu since the first restaurant opened in the Lakeview neighbourhood in 2009, said David Morton, co-founder of DMK Restaurants, which operates three of the burger joints in the Chicago area, as well as locations in Soldier Field. "They have a very, very loyal following."
Most of the US crop is grown in the Southeast, where land has traditionally been used for tobacco and cotton. More than half comes from North Carolina. Total domestic output last year jumped 4.8 per cent to 14 billion kg, the highest since 1946, USDA data show.
Seedings this year are forecast at the highest since 1965, the USDA estimates, providing a profit boost to farmers at a time when global surpluses of grain and oilseeds have led to lower prices and losses on those crops. A farmer can generate US$1200 to US$1400 of operating income per acre growing sweet potatoes, up from US$827 in 2012, according to an analysis by Elizabeth Canales, an assistant professor of agricultural economics at Mississippi State University. By comparison, US farm income is falling for many crops, and some Midwest corn growers may barely break even.
Demand growth domestically is partly driven not by raw sweet potatoes but value-added products like pre-cut cubes or fries, said Jennifer Campuzano, a Chicago-based director at Nielsen's Perishables Group, which tracks food consumption. While retail sales climbed 3.2 per cent by volume in the year ended April 30, outpacing a 2.6 per cent gain for all produce, value-added products rose 18 per cent, Nielsen data show.
China is by far the biggest consumer and produced 70.5 million tonnes in 2013, more than 20 times any other country, according to the latest United Nations data. But demand for US exports is being driven mostly by increased sales to Europe, including the UK, Netherlands, Belgium and Ireland. Exports last year of 179,881 tonnes were more than double those in 2010, and sales in the first five months of 2016 are running 24 per cent ahead of the prior year's pace, according to USDA data.
"It has certainly got more popular than it used to before because maybe we finally worked it out how to cook it properly," said Scott Hallsworth, owner of Kurobuta, a Japanese restaurant in London, where he serves sweet-potato fries. "People don't realise how versatile it is."
At Habanera, a Mexican restaurant in London, owner Lorraine Cais said she's using more sweet potato because it "marries very well with hot and spicy Mexican food and offers us a chance to challenge ourselves, innovate and get more flexibility in designing our dishes with it, unlike regular fries, which are boring."