this is usually a house plant.. there is a house plant forum.. where you might get a wealth of knowledge... otherwise i care not where you post ...

these things root in water.. in about 20 minutes.. i dont know why you would want to deal with seed ...

root some pieces.. grow them indoors for winter ... come 6 weeks before last frost.. root up a dozen of so cuttings.. getting them ready to take outdoors .. when weather allows ...

many tropical or semi-tropical house plants.. may not make viable seed.. simply because the season.. up here. .. is not long enough for the seed to ripen ...

WAG'ing here.. so maybe i am wrong

ken

First, want to make sure, you're talking about Gynura? Was your plant outside when it flowered? Theoretically, if bees or moths or some critter pollinated the flowers, they should make seeds. But not all flowers make seeds, plants can be self-sterile, seeds are viable but produce species instead of hybrid or cultivar, or any number of issues with seeds in general could be possible from there.

Aside from confirming those basics, it's not something I've heard of being done before. Anxious to hear more also.