Why your salad needs a pinch of this bitter herb—arugula adds flavor depth, boosts digestion, and transforms boring greens.

Maror refers to bitter herbs eaten during the course of the Passover meal, once on its own and once together with matzah, Chabad.org said. The first time it is eaten a special blessing is said.

It’s bitterness. Specifically, the strategic use of arugula, that peppery, slightly bitter green that delivers a flavor punch far beyond its delicate appearance. While many home cooks shy away ...