Sunflowers signal their readiness in several ways. The easiest to see is that the ripe seeds start falling out. Pick up a few and split them open to see if the seed is plump with meat, or watch the neighborhood squirrels – they never miss an opportunity for an easy meal.
Bagging the head with perforated plastic bags will help keep birds and squirrels from pilfering, but if you want to harvest before you start losing seeds, look for the heads to be droopy and down turned with the back changing from green to yellow/brown. Petals will be shriveled and falling, leaving the plumped seeds exposed.
At this point – before the seeds start falling – cut the head off the stem, leaving one foot of stem attached. Hang them upside-down in a warm place until dry and the seeds separate easily. Then use this stem to turn over and hold the head upside down while rubbing the seeds out by hand. Dry and store them or roast them in a 300 degree F oven for 15-25 minutes.
If you prefer your seeds salted, soak them overnight in a brine of 2 tablespoons of salt to 1 cup of water. Boil the brine, seeds and all, for a few minutes, drain, then spread them thinly on a cookie sheet and roast in a 200 degree F oven for 3 hours or until crisp. Roasted long enough, they’re easy to shell.