Spinach. ホウレンソウ、ほうれん草, 菠薐草 (Spinacia oleracea).
Spinach is an edible flowering plant, with a high nutritional value and rich in iron. Spinach originated in central and southwestern Asia, perhaps ancient Persia, and was brought to East Asia via the Silk Road. It reached China already in the 7th century, where it was called "Persian vegetable," but Japan had to wait for spinach until the 17th c. It is said that the famous warlike daimyo Date Masamune loved spinach.
Spinach today is a favorite vegetable in Japan (Japan is the top third spinach producing country in the world, after China and the U.S.), although the way it is used differs greatly from Western cuisine. It is most popular in a cooked salad (aemono) called horenso no goma-ae, that is: cooked spinach dressed with sesame seed. It is also excellent in o-hitashi, parboiled and soused in dashi with soy sauce and mirin, and served chilled. Besides that, spinach is used in soups.
[Horenso no goma-ae, Cooked spinach salad dressed with sesame]