“Anybody gone into Whole Foods lately and see what they charge for arugula?” asked then-Sen. Barack Obama, during an Iowa campaign rally in 2007.

If arugula—excuse me, rocket—were to gain the American dietary prominence it so richly deserves, it would probably be relatively simple for the country’s farmers to keep up with the demand.

As a leafy condiment, our pungent green has a lot going for it. It stays stiff and crunchy long after harvest, yet remains tender. Arugula has been a staple for centuries across Europe, with ...