Seed Saving- Sunflowers When the sunflower seeds are fully formed harvest the whole flower head. You can knock off a few flowerettes to check if it’s ready for harvest. Our resident Scrub Jay got a head start on this one! Watch the birds. They’ll tell you if the seeds are ready! Knock off all of the old flowerettes covering the mature seeds. Then, start picking out those seeds. They are so tasty when they are fresh! A Mammoth Sunflower gets saved for next year.