I have been germinating Carnations, Siberian Blues and Sweet William seeds in large pots and donít appear to have problems other than too many seedlings. I had been purchasing large ornamental pots from Lows for about $8.00 but have now taken to buying large used commercial ports from my local garden center for $2.00 or less. I am finding that by using pots it is easier to inspect the seedlings.
I have not observed any seed predation on Dianthus. Last summer I neglected to make arrangements to have my garden watered while on vacation and thought I lost one pot of seedlings. A month later, the Dianthus made a comeback, survived the winter should be blooming in 4 to 6 weeks.
Why donít you try the following experiment? Everyone at DG has an extra large pot or two lying about. Using out of the bag potting soil, try growing Dianthus in a pot and in the garden. If the pot works you probably have something in your garden which likes Dianthus seeds or seedlings.