when the flower fades if there are any seeds the dead head will continue to swell as seed forms. when the head dries you may be lucky and have seed. when the head is dry shake/scrape the seeds out of the dead head and keep in a paper bag/envelop until spring.

many double flowers wont produce seed as the sexual parts are turned into petals.

I wondered if that's how to try saving them..so it's similar to how you save Poppy seeds then ? All mine are single ones,so I'll give it a try.thank you Eileen .:o)

the seed head is more like a centaurea / marigold where the seeds cling to the old flower head.

Ah,I see.I think I get it now.thank you ..