I don't recall planting this guy. It is over 8 feet tall and just started blooming last week, first of September in Connecticut. I suspect it to ba a variety of sunflower but would love to know and to know if I dry seeds if I can propogate. Thanks
I don't see why not. Just make sure the seeds are fully ripened - for an autumn-flowering perennial that usually happens as the plant is going dormant after a good frost. Don't know about H. maximiliani specifically, but the seeds of most hardy perennials germinate best if planted in autumn/winter and allowed to chill in the ground over the winter (which is what happens naturally when the seeds fall to the ground).
Another way to propagate would be by dividing the roots. The native perennial sunflowers, such as H. maximiliani, angustifolius, and salicifolius have rhizomatous/stoloniferous root systems and can spread quite aggressively in favorable conditions. Just dig up and transplant part of the roots after frost/freeze kills the foliage. But be careful to plant it only where you won't mind if it goes wild. (I made the mistake of planting H. angustifolius in my garden... the first year it was nice... after that it kept popping up everywhere and by the 3rd year I decided I'd had enough and spent the next 2 years trying to get rid of it.)
Goldfinch love these and will hang upside down to get to the seeds. The seeds are pretty tiny as far as sunflowers go. If you want seed make sure the finch do not get to all of them. I grew these in Alabama and brought seeds back to Illinois and grew them in pots the first year. They are not as aggressive in this zone, but I love them and the color they give when most other flowers are gone or few.