I have the Irish form of D.rotundifolia growing outside here in Ireland, the seed will even germinate right after the seed ripens in the autumn, the flower stack falls over and the seed germinates in the pods. Of course even more germinates the next spring, my bog garden has lots of D. rotundifolia and D. intermedia (I think) and they are very easy to grow and flower and reproduce. I have some D. rotundofolia seed in the fridge if anyone wants some, its kind of old though. I'm going to collect some more this year.
I don't have any D. anglica although that's native here too, I've never seen it.