Hi,
Dianthus seeds are not that tiny. They are black or dark brown little chip looking things. On the link below, there is as pic. The size looks about right on my monitor.

Here is a link that might be useful: Dianthus Page on The Seed Site

Remy, thanks very much for the response. I waited until the pods were very dry but no seeds like the ones you posted. Guess I'll work on the timing and see what happens next year. These were patented plants - could they be sterile? Margie

They could be sterile. I had a sterile variety so I know they are out there. Usually dianthus make seeds in abundance. Another reason for no seeds could be if the weather was odd during bloom time. Very high heat will cause plants to not have seeds. Excessive rain can do the same.
Remy

This past Spring I purchased a whole flat of beautiful red dianthus. They were small, like they may have been sold as plugs. They have been planted in the flowerbed and still aren't much larger than when I planted them in the Spring. Is there any hope that they'll grow larger. If not, they can go in the yard waste bag that they collect on Mondays or Thursdays. They are taking up valuable real estate!

Margie - do you want some dianthus seeds to winter sow? I harvested all the seeds from my various perennial dianthus and marked them (can you believe it?) so they're separated by cultivar name. There's way more than I'll be able to WS this time around so they're yours if you want them (for postage). I do WS dianthus every year but may finally be closing in on having enough of them. (;-p)

I waited until the pods were very dry but no seeds like the ones you posted. They may have fallen out or been eaten.