I'm fairly certain you are referring to Dianthus amurensis, which is a great summer-flowering species, but is also relatively short-lived.

They enjoy full sun in well drained soil. They won't tolerate wet soil and especially in winter. I grow mine in mostly sun with late afternoon shade and in full sun and they both do well. If you deadhead they will bloom a lot longer. I also find their seed easy to collect and can be easily winter sown for fresh plants anytime you want them.

Here is a link that might be useful: Dianthus Care