Found this info from the U of IL:
Harvesting & Handling Sunflowers
Sunflowers growing in the backyard are easy to harvest and roast for a tasty treat. Sunflowers should be allowed to mature in the garden. There are several indicators of maturity. The back of the flower head will be brown and dry; most of the yellow petals will have dried and fallen; the seeds will be plump; and the seed coats will be black and white striped.
When the seeds are ready, but before the seeds begin to loosen and dry, cut the head off the stem leaving about one foot of stem attached. Rub the seeds out on the head by hand, dry, and store.
If birds and squirrels harvest your sunflowers before you do, you have a couple of options to discourage the critters. Cover the heads with paper sacks so the seeds are harder to retrieve. Heads may also be picked when the back turns from green to rich yellow, and then dried in a dry, protected location.
If your seeds are for the birds, store them sealed containers in a dry spot.
Sunflower seeds are good as a snack or added to favorite recipes in place of nuts. Raw mature sunflower seeds are easy to prepare at home. Cover unshelled seeds with salted water. Use 1/4 to 1/2 cup of salt per two quarts of water. Bring to a boil and simmer for two hours. Drain and dry on absorbent paper. Seeds may also be soaked overnight in a salt solution.
Roast sunflower seeds in a shallow pan at 300 degrees for 30 to 40 minutes or until golden brown, stirring occasionally. After removing from the oven, stir in one teaspoon of melted butter or margarine for every cup of seeds. Cool on an absorbent towel and salt to taste.
One-quarter cup of sunflower seeds is 200 calories. Sunflower seeds are high in potassium, calcium, and phosphorus.
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