This tall annual sunflower produces 4.5-inch pale, butter yellow flowers with dark brown centers throughout the summer. Side branches are long stemmed and provide a succession of flowers once the terminal flower sets seed. The pollen-less flowers are a favorite of florists. The longer-than-normal flowering season is due to its day-neutral flower bud initiation—in other words, it doesn't have to wait until after the summer solstice to flower.