Non-GMO, Heirloom Green Wave Mustard Seeds from True Leaf Market. Green Wave Mustard is a terrific all-purpose mustard green. Its bright green ruffled leaves have a moderately hot flavor. Cooking mellows the flavor. From baby leaf to full size, this mustard seed is reluctant to bolt in the heat and also has excellent cold tolerance. Mustard greens originated in India and have become common throughout the world.