It’s inedible and highly elusive — and San Francisco bartenders can’t get enough

For a few short weeks every spring, San Francisco chefs and bartenders race to get their hands on ume, a tart Japanese plum with skin the color of a tennis ball. It’s not because they’re good to eat; in fact, they’re inedible raw. But once the golf-ball-size fruits have been coated in sugar and steeped in spirits for at least half a year, the infusion becomes one of the most sought-after cocktail ingredients of the moment: umeshu.