Sunflowers brighten a garden with vibrant warm colors and flower heads that follow the sun, yet they also supply food to humans, birds, livestock and small mammals. Harvest sunflower seeds after the plants reach maturity, which is approximately 90 to 100 days from planting, according to the University of Missouri Extension, but may vary by location and sunflower variety. Check the seed packet to determine its growth rate and harvest time, or observe the sunflowers and their seeds for seasonal changes that indicate seed maturity.
Monitor the seeds and flower heads; the petals die away and the flower head's backside dries and turns brown when it's time to harvest the plump, white-striped seeds.
Cut the stem at approximately 1 foot below the flower head, as suggested by the University of Illinois Extension.
Hang the flower heads by their stems with wire or string in a dry, well-ventilated area. This is not necessary if the seeds loosen readily by rubbing them with your hand; if they do, spread the seeds out in a single layer to dry before storage.
Cover the flower heads with paper bags to catch the seeds as they dry and fall from the head, as recommended by Colorado State University, and then roast them or store them in an airtight container to feed wildlife.