40 to 50 Days to maturity. Brassica juncea var rugosa. Miike Giant Mustard Seeds. Non-GMO, annual heirloom. This broad-leafed, ruby-veined, loosely-headed mustard actually gets pretty big! It can be up to 18 inches tall and needs a bit more space than many other types of mustard. It is good for spring or fall planting. In cooler climates, it can be grown to full maturity in the spring, but in warmer areas, it should be grown in the fall for full growth. A perfect addition to a bountiful spring or fall garden harvest. Approx 18,400 seeds / oz.