Hong Kong Choy Sum is a leafy vegetable commonly used in Chinese cuisine. Choy sum is a transliteration of the Cantonese name, which can be literally translated as "heart of the vegetable".

Choy sum is a green leafy vegetable similar to Kai Lan, and can be characterized by the distinct yellow flowers which it bears. Each flower has four yellow, oval to round petals with six stamens on fleshy, erect stems, and are oval with slightly serrated margins leaves, which never forms compact heads like the cabbage.

The height of the plant varies greatly, ranging from 10-40cm depending on the growing conditions and the variety.