An amazing giant heirloom sunflower with enormous blooms, up to 1 ft across. The large yellow flowers with brown centers top plants 9 to 12 ft tall and yield heavy loads of seeds. Fast and easy to grow, Mammoth sunflowers are great for creating a sunforest for kids, a tall annual hedge or screen. Sow in the spring after the last average frost date. When around 3 in tall, seedlings should be thinned to 2 ft apart. Edible seeds attract birds and make great snacks. To save seeds, cut the stem beneath flower heads when the backs of the flower heads turn yellow. Hang upside down and let dry in a cool, dry place for about a month. Cover with netting or a paper sack with holes to keep seeds from falling.