Late blooming plants

I'm wondering about New England Asters which bloom in September-October. Do they propagate by roots or by reseeding?

New England asters can be started from seed, but 60 days stratification is recommended. I almost successfully started some last year, but they took so long to germinate, long after everything else, that I gave up on them. By the time I looked into their covered tray again, they had come and gone. Hopefully, I'll do better this year.