30-40 days. Amaranthus mangostanus. White Leaf Amaranth Seeds. Non-GMO, annual, heirloom, open-pollinated. This crop is suitable for containers, garden plots, raised beds, and fields. Also called Chinese spinach, this heat-tolerant leafy amaranth yields tender, pale green leaves and stems for quick sautéing and soups—vigorous even in summer heat. ~27,000 seeds/oz.