I planted a row of this pink Dianthus about three years ago in my front garden, thinking that they are annual flowers, and that was what it said on the pots too. However, they are perennial flowers to my surprise.
They come back every year, and it seemed that the pink color is getting deeper as each year goes by. When one group of flowers died, another group took their place, and they kept on flowering.
I like hardy flowers and the Dianthus are very easy to take care too. I just have to water them every other day, and they are happy. They seem to thrive in my "clay" soil, and very tolerance in hard sun.