Komatsuna (小松菜) or Japanese mustard spinach (Brassica rapa var. perviridis) is a leafy vegetable and is a variety of Brassica rapa, the plant species that yeilds the turnip, mizuna (水菜), napa cabbage and rapini. It’s grown commercially in Japan and Taiwan. In Japanese cooking,it is stir-fried, pickled, boiled, and added to soups or used fresh in salads. It’s rich in calcium.