Ligularia do make viable seed. Not all the seed they make is viable though. You have to look for the bigger plump ones. The others never matured. So you need to collect from multiple dead flower heads to ensure having enough seed. Seed collected from a cultivar may have babies that vary from the mother plant as opposed to a species ligularia which will produce babies pretty much all the same.
Remy

Thanks for your reply. I don't mind if they don't come true, I just want more ligularias that didn't cost $15 each. :0)

I started harvesting them. Out of two whole seed heads, there was only a single developed seed. The rest were empties. I'm going to leave the others as long as possible and hopefully get a few more.

The is an old post, but I'd like to provide a clarification for, er, posterity:

Ligularia seedheads will produce at best only 1-2 viable seeds, no matter how long you leave 'em. The rest will remain puny, immature and useless. I've attached a pic of a viable seed and non-viable for reference. The viable ones really do stand out.