Congratulations and kudos!! I do believe you may be the first person to successfully harvest/sow/grow D. spectabilis from seed. I checked my D. spectabilis 'Alba' for seedpods last year but was unsuccessful when looking for any that were ripe. Did you harvest the seedpods right when they fell from the plant stems or while they were still attached & green? Do please describe your strategy so that others may attempt to learn from your success.

I'm pretty sure some people on Winter Sowing have done this. Also I think several people have said they get self sowers. Anyhow, I just watched the pods very carefully and put small paper bags on them when they looked as if they would soon split open. I caught the seeds and just sowed them shallowly in some commercial seed compost in a pot which I then left outside in my garden for the rest of the year. No fancy techniques.