Arugula greens consist of vibrantly green colored, deeply lobed leaves attached to a pale creamy-green hued stem. The leaves can be harvested when young for a mild flavor or when fully mature at 3 or 4 inches in length for maximum mustardy tones. However, those leaves allowed to mature too long on the arugula plant will become bitter in taste. Arugula offers an herbaceous, peppery flavor with a mustardy tang and nutty finish.
The pungent flavor is due to its high content of sulfur containing compounds known as glucosinolates. The leaves are commonly used as a salad green or herb in fresh sauces such as pesto.