90 Days. Peppermint Culinary Herb Seeds. Mentha x piperita. Non-GMO. Heirloom. A deliciously versatile and bright herb, peppermint seeds are a naturally occurring hybrid between culinary spearmint and watermint. Grown very similar to basil, peppermint seeds mature to 12-18" tall and wide, ideal for patios and container gardening. Although delicate in flavor, peppermint seeds can be a very aggressive spreader when grown in the garden bed. Approx 336,000 Seeds per Ounce.