8-12 Days to maturity. Brassica rapa subsp. chinensis. White Stem Pak Choi Microgreen Seeds. Pak Choi is a popular microgreen as it is easy to grow, mild in flavor, and adds a delightful and fresh crispness to anything it is added to. Because it is mild in taste, this is a great variety for introducing kids to micros. Keep a batch of these on hand for boosting the nutrients of your everyday meals, or adding a flash of spring green with these dainty leaves and thin white stems. ~6,000 seeds/oz.