These young leaves of the prickly ash tree have a fresh, subtle mint flavor and a tender texture. They're occasionally available fresh in Japanese markets during the spring. Kinome is used as a garnish for many Japanese dishes. Store the fresh leaves in a plastic bag in your refrigerator's vegetable drawer. They should be used within 3 to 4 days. Though watercress or mint can be used as a substitute for color, nothing can duplicate the flavor of kinome.