Hi there,
I grew some similar ones some years ago (branching ones, different cultivar).
Saving seed is tricky, competing with all kind of birds and things,
plus you need to make sure that it is not a hybrid, in which case it wouldn`t come true from seeds.

Otherwise, if you want to keep them flowering, keep deadheading, watering and- if in doubt- fertilizing.
That worked for me on sandy soil.

Hope that helps, bye, Lin

Thanks Lin..! I can understand that birds might get the seed before I would and I do think it is a hybrid, so probably wouldn't know what I'd get. Thanks, I'll do that. Saturday tomorrow, I am trying to use up as much of my Fish Emulsion/Seaweed fertilizer before the growing season is over, so that's a good suggestion. I should be able to keep it going for at least another month.

It did help, thanks! Bye..