Brassica juncea

Brassica juncea is a species of the mustard plant. It is commonly known as mustard greens, Indian mustard, Chinese mustard, Kai Choi, and leaf mustard. Originally, it came from Asia, but it has also been imported into other parts of the world. 
Its leaves are commonly used as a vegetable. Its flowers can also be eaten raw, or cooked. Its seeds can be pressed into a vegetable oil or used as a kind of spice. The seeds are also used to make culinary mustard, especially Dijon mustard.