On New York City’s Upper East Side, it’s difficult to walk two blocks without running into at least one salad spot. Packed with hungry lunch crowds and bearing similarly evocative names, it can be hard to tell them apart: Fresh&Co is on Lexington Avenue and 85th Street, and Sweetgreen is one avenue directly east. Two blocks south there’s a Just Salad; a couple more, and there’s Chopt.

While Manhattan’s concentrated geography is ripe for exaggerated examples, fast-casual salad chains are increasingly becoming ubiquitous in many cities across the country, thanks to the coalescence of two trends: an overall boom in fast-casual dining, and a cultural shift toward healthier, vegetable-heavy meals. “It’s the perfect moment,” says Aaron Allen, a restaurant industry analyst. “Fresh is the most bankable word in food service.”

Sweetgreen, the current superstar of the space, raised close to $100 million over the past 10 years and opened 20 new locations in 2017. And while its reputation is as big as its bank account, salad chains with less buzz are spreading out, too: Houston-based Salata, for example, expects to top 100 locations by the end of 2018. Meanwhile, an array of investors, from hospitality giant Danny Meyer to NFL players, are lining up to get in on the greens, while celebrity chefs are signing on for menu collaborations.

Where did all of this hunger for salad-at-scale come from, and how are the major players differentiating themselves at and beyond the counter? Beyond that, which chains are destined for success — and which others will be tossed out?

The fact that office workers wait in long lunchtime lines while proudly holding their reusable bowls (which shout, “I’m a regular!”) outside a restaurant called Just Salad is fairly remarkable when considering salad’s cultural reputation for much of the past few decades. Americans historically associated salad with deprivation, relying on an outdated stereotype of women on diets abstaining from ostensibly tastier, more satiating options.

In the second half of the 20th century, the creation of self-serve salad bars at steakhouses and other family dining institutions like Ruby Tuesday and Sizzler started to change that. Self-service salad bars became popular at corner delis, too, pushing salad into the “fast” category. But as Florence Fabricant noted in the ’90s, instead of turning people on to the vast culinary possibilities of vegetables, these so-called “salad” bars twisted the definition of salad to include things like lasagna, barbecue chicken, and, of course, Jello.

The entrepreneurs fueling the current fast-casual salad explosion set out to tap into enthusiasm for the Chipotle model — let diners customize their meal, but assemble it for them while they watch — while attempting to shift the perception of salad from “diet food” to a desirable, filling (and yes, trendy) meal.

“Taking that first step, to open a salad-only restaurant back in 2001, was a huge risk,” says Tony Shure, who opened the first Chopt with co-founder Colin McCabe in New York City’s Union Square, long before all of the other players hit the scene.

Soon after they opened, Shure and McCabe were overwhelmed by the lines outside Chopt, which stretched down the block at lunch. They felt they had found an untapped niche.

From the beginning, Chopt marketed itself as using “better ingredients” (even, in a true but convenient marketing ploy, weaving in a legend about turning down a batch of vegetables that would have saved them $75,000 because the quality wasn’t up to par). But it was Sweetgreen, which launched in Washington, DC in 2007, that first turned lettuce in a bowl into a full-on lifestyle brand — mimicking the social media savvy and real-life event marketing of Red Bull, which at this point might be known as much for its extreme sports sponsorships and stunts as it is for making an energy drink.

“One of the realizations we had was if you looked around, all of the coolest food was the least healthy,” says Nicolas Jammet, who created the Sweetgreen concept in his Georgetown University dorm room with classmates Nathaniel Ru and Jonathan Neman. “Part of building this brand was to change that and... have it be the coolest food,” Jammet says.

From 2010 to 2017, the company hosted an annual music event called Sweetlife Festival, leading to collaborations with artists like Kendrick Lamar, whose “Beets Don’t Kale My Vibe” salad was a huge seller. Then there are the celebrity chef partnerships: During Dan Barber’s food waste-themed pop-up, Wasted, the owner of the acclaimed Blue Hill restaurant in New York created a special salad for Sweetgreen’s menu that featured cabbage cores and carrot peels; currently, the restaurants are serving a fast-casual version of LA-based chef and baker Nancy Silverton’s signature chopped salad.

Sweetgreen’s initial expansions focused on other East Coast cities like Philadelphia, New York, and Boston; in 2015, its first West Coast branch opened in West Hollywood, and it now has 15 stores in California. Sweetgreen hires “community ambassadors” in each city to promote the brand and organize events for fans, such as fitness classes and farmers market outings, and it appears to be working: “There’s definitely a special cache around Sweetgreen in Los Angeles,” says Jordan Shakeshaft, an editor in LA who covers health and wellness. “They... appear to be the go-to caterer for wellness-related events around the city. I rarely find myself at a fitness event where I’m not fed a Sweetgreen salad afterwards.”

By marketing their product as a component of an aspirational, Instagrammable lifestyle rather than mere bowls of lettuce and vegetables, chains like Sweetgreen have also convinced diners to pay more for their desk lunches: Bowls typically cost between $9 and $15, depending on proteins and other add-ons.

A post shared by sweetgreen (@sweetgreen) on Jul 21, 2017 at 3:05pm PDT

Sweetgreen’s quasi-locavore approach also adds to its perceived value. Today, one section of Sweetgreen’s menu changes five times a year based on what’s in season, and different regions serve slightly different food. The Harvest Bowl on the East Coast, for example, contains apples; on the West Coast, it’s called the Hollywood Bowl and has jicama instead. Co-founder Ru says even the same menu items can taste different based on the region, since ingredients are sourced from different growers and climates. “We want people to understand that that’s normal and that’s okay,” he says. “Something should taste different in a different place.”

That’s a major shift away from traditional fast-food principles, which dictate that customers should be able to walk into any location and get the exact same food and experience. In this realm, each chain is constantly trying to prove it’s more connected to farmers than the other guy. (Fresh&Co even bought its own farm on Long Island, announcing it would provide “hyper-local seasonal” ingredients.)

Sweetgreen’s arrival in LA put it in the home turf of Tender Greens, a chain that gets lumped into the fast-casual salad category despite the fact that its top-selling menu item is called the Backyard Steak Plate.

“We bump into Sweetgreen because of the name. There’s this natural tendency to say, ‘Oh, are you like Sweetgreen? Or are they like you?’” says Tender Greens co-founder Erik Oberholtzer. “[We] say, ‘No, it’s totally different,’ but we do bump into them.”

Whether it belongs firmly in the same category or not, Tender Greens is certainly serving a similar customer. There are 26 locations spread out across California, and in February, the first East Coast restaurant opened in Manhattan. The jump across the country was made possible via restaurateur Danny Meyer’s “strategic minority investment“ in the company (the exact amount of which was not disclosed) and on-the-ground guidance from his Union Square Hospitality Group team. Additional locations in New York and other East Coast cities, including Boston, will follow. (Meyer also announced an investment in Sweetgreen in 2014.)

An emphasis on culinary credentials, however, is what Oberholtzer — a chef who once worked for the farm-to-table pioneer Alice Waters at Chez Panisse — says sets Tender Greens apart.

“For me, the defining characteristic is that there’s a real chef in the restaurant,” he says. Tender Greens’s new Manhattan location emphasizes dining in. Diners may order their salads standing up, but they’re more likely to eat them seated with a glass of wine.

Another burgeoning Cali success story is Greenleaf. With just eight locations in Los Angeles and Orange County, it’s tiny compared to many of the other chains. However, it’s carefully curated a lifestyle image for itself — think t-shirts that say “Fresh AF” — that appears to be working; industry experts including Allen reference it as an up-and-comer. (It helps that founder Jonathan Rollo is married to cultish boutique fitness studio chain Barry’s Bootcamp CEO Joey Gonzalez, creating a muscled marketing match made in heaven.)

But ask salad-obsessed millennials which chains speak to them, and Sweetgreen seems to come out on top. “If I didn’t have a full-time job, I would be a salad connoisseur,” says 23-year-old Kate Kerner, who “tends to go every day” to Sweetgreen for lunch, she says, but “also loves Chopt.” Clair Rachel Howell, a 21-year-old actor, says she “also loves” Just Salad, but given a choice, she’ll choose Sweetgreen every time. “Honestly, I really just like their brand, I like their aesthetic, I like the inside of their restaurants, and I think they have more interesting options,” she explains.

Fueled by venture capitalist funding, Sweetgreen has also been out ahead of the pack in incorporating technology into its business model. Forty percent of the company’s orders are placed through its app, and it’s working on experiments with blockchain technology to ramp up the quality of its ingredients.

Though it doesn’t have the same brand awareness, the true tech bro of the salad world might be Honeygrow, a Philadelphia-based chain that’s opened nearly 30 locations in eight states in just a little over five years. Honeygrow’s ordering and customization all takes place on screens set up in front of the line; customers select the ingredients they want and swipe their credit cards without human interaction, though employees still assemble the food in front of customers. The simply system makes ordering fast, which seems to lend itself to scaling up quickly.

So are chains like Sweetgreen on their way to becoming household names like Chipotle or Panera? Not likely, according to NPD Group restaurant industry analyst Bonnie Riggs. “Is there a market for this kind of concept? Yes. Is the market huge? No,” she says. “It’s very well-received and popular in major metropolitan areas... but it’s not particularly appealing to middle America.”

Riggs notes that while the overall fast-casual space had been growing by seven or eight percent annually for several years now, industry sales data for the end of 2017 indicates growth has finally slowed, to four percent year-over-year, “and that’s quite a change. We are seeing more of these concepts coming on the scene, but we’re also seeing that we still have more supply than demand.”

That will likely lead to closures as individual brands continue to grow and compete: Before the end of 2018, Sweetgreen plans to introduce a “3.0” restaurant concept and launch delivery; Tender Greens is expanding on the East Coast with two Boston locations, one planned for April and another for August. Meanwhile, Just Salad is planning expansion into new cities, and Salata is planning to open more than 30 additional locations in Florida and other new markets.

“I think both Sweetgreen and Tender Greens are way out in front and have enormous potential,” Allen says. All of the chains will face major challenges related to the supply chain, like waste and cost control, since sourcing fresh, local food at scale is much more complex than using mass-produced, processed ingredients like traditional fast-food chains.

Still, Riggs says that in a category like fast-casual salads where urban millennials and Gen Z are driving demand, locally sourced ingredients can be a strong competitive point of difference. In fact, while growth in the fast-casual market has slowed overall, according to Riggs, cities that showed the most growth in the space shared one major characteristic: a strong local food movement that emphasized connections between farms and restaurants.

In the end, “one of the biggest challenges is going to be differentiation,” Allen says. “There’s only room for so many brands in a customer’s mind... and there’s really a lot of ‘green’ out there.”

Lisa Elaine Held is a journalist based in New York City who covers the intersection of food, health, and sustainability.

Editors: Whitney Filloon and Daniela Galarza