We planted some sunflowers this year though only one really bloomed very well. But now that they have died off what should I do with the heads? Can the seeds be kept and planted again next year or should I just dump them? Do they need to be prepared in any way?
A lot of sunflowers are grown around here and after harvesting the birds eat most of the missed seeds. However many germinate next year to produce a 'volunteer' crop, they even grow on the road verges.
You could try planting them next season, but most sunflowers, at least here in the U.S. are the product of hybridization and aren't likely to sprout and if they do may be something entirely different from what you planted (some other variety of sunflower).