Sijiu choi sum is a common early-maturing, heat-tolerant variety of choi sum.

Sijiu choi sum is an early-maturing variety of choi sum, widely cultivated in South China and especially common in the Guangdong area. It is generally believed that its name is related to its relatively early harvest period; the time from sowing to harvest is short, making it a representative of fast-growing leafy vegetables. Compared with mid- and late-maturing choi sum, it is more heat-tolerant and is an important choice for summer and autumn cropping.

In appearance, the Sijiu choi sum plant is on the small side, with yellow-green or blue-green leaves and uniform blue-green flowering stalks that are crisp and tender, low in fiber, and have a sweet, fresh flavor. Choi sum is roughly divided by maturity into early, mid- and late-maturing types, and Sijiu choi sum is a common variety among the early-maturing types. Its marketable part is mainly the tender stalk, commonly known as the choi sum stalk.

For cultivation, it is mostly direct-sown, either by broadcasting or drilling, and seedlings should be thinned in time after emergence to keep good airflow between plants. It likes moisture during the growing period, so light, frequent watering is appropriate, avoiding alternating drought and waterlogging; fertilization should be based mainly on basal fertilizer, with a light top-dressing before harvest. In summer heat, pay attention to shading and cooling, and watch for pests such as aphids and cabbage caterpillars; it can also be grown in pots on a balcony, choosing a spot with ample light and using loose, fertile soil.

Harvesting depends on the maturity of the stalk; generally, when the stalk height approaches the top of the leaves and the flower buds first appear, pinching it off is most suitable, while delaying tends to make it age and the fibers thicken. After harvesting the main stalk, the plant can still sprout side stalks, allowing harvest in batches. For eating, the most common methods are blanching, plain stir-frying, stir-frying with garlic, and cooking in superior broth; it is crisp and refreshing, a seasonal green leafy vegetable on home dining tables.