40 Days to maturity. Brassica rapa var. chinensis (33 days) Organic White Stem Pak Choi Seeds. Who can resist Baby Pak Choy! This is White Stem or 'Baby Bok Choy', the famous Asian green. It is often referred to as a nai pe tsai type or dwarf type with white spoon-shaped petioles and dark green glossy leaves. This variety grows best in mild climates and can tolerate heat. It can be grown year-round in sub-tropic areas.