41 days to maturity. Brassica rapa var. japonica Mibuna Green Spray Mustard Seeds. Non-GMO, warm or cool-season, annual, hybrid. Similar to mizuna greens, mibuna mustard is a flavorful Japanese green strap leaf mustard with a mild mustard flavor. Although it is very similar to mizuna, differentiate mibuna by its smooth, pointed leaves and distinct flavor. Although not as tenacious as mizuna, mibuna produces a slightly stronger and more complex culinary mustard profile and an attractive display of foliage. Mibuna greens are a cold and heat tolerant crop suitable for all gardens. Approx. 7,500 seeds per oz.