Wiktionary
tatsoi
n. (taxlink Brassica rapa narinosa subspecies noshow=1) or (taxlink Brassica rapa var. rosularis variety noshow=1), an Asian variety of ''Brassica rapa'' grown for greens, lately popular in North American cuisine.
Wikipedia
Tatsoi
Tatsoi (Brassica rapa subsp. narinosa or Brassica rapa var. rosularis) is an Asian variety of Brassica rapa grown for greens. This plant has become popular in North American cuisine as well, and is now grown throughout the world.