40-50 days to maturity.Brassica rapa var chinensis. Chun Yu Hybrid Pak Choi Chinese Cabbage Seeds. Non-GMO, warm-cool season annual, hybrid. This is a medium size shanghai pak choi hybrid with medium maturity. The plant has a compact shape with dark green leaves and short petioles, good tolerance to heat and cold, and is very slow to bolt. Chun Yu is suitable for spring, summer, and fall planting. It can also be used as Shanghai Pak Choi and Shanghai Miao. ~ 6,000 seeds per oz.