Agrostemma White Agrostemma Githago Bianca is an annual native to Mediterranean region, and White Agrostemma can be easily grown from seeds. Also called Corn Cockle, this Agrostemma has tall slender hairy stems with long, narrow leaves and produces large 1.5 inch in diameter, satiny, white flowers with radiating black dotted lines. Agrostemma blooms from mid-spring to mid-summer attracting bees and hummingbirds to the garden.