Posted: 04/07/2013 at 22:21
My understanding is that they are biennual plants so once they flower that's it, their life cycle is complete. I think they are fully hardy so any plants grown from seed this year, will withstand the winter and flower next year, Not sure what you mean by flagged..........do you mean when the flowers are over and seeds are forming?
I've known some that self seed so almost become perennial.
Out of interest the leaves that made it through, are they the ones that are due to flower soon?
You can collect seeds once they have flowered, I would sow them straight off the plant once they are dried enough, that way you should be able to plant them out before the first frost and they will grow next year.
Hope that helps a bit