Choy sum (also known as vegetable heart or菜薹) is a vegetable species with the scientific names Brassica rapa var. parachinensis or Brassica chinensis var. parachinensis. It is characterized by its green stems, small leaves, and deep green leaf blades, with small yellow flowers appearing between the leaves. Choy sum is a distinct variety primarily produced in Guangdong Province, China. Its English name, "Choy sum," is derived from the Cantonese pronunciation.