No dianthus are perennials meaning they grow back each year. Some need trimming and tidying up, we prune ours when they have finished flowering. They can be lifted and divided every few years.

If you want, you can increase stock even faster by taking cuttings right now. These can be selected from none flowering shoots. Just pull gently holding the base of the stem (so you don't pull the whole plant out) until a shoot snaps cleanly at a joint. Ideally with about 6-8 pairs of leaves. Remove the lowest and place around the edge of a clay pot in gritty seed compost with a poly bag over them. Place in light shade outdoors and six to eight weeks later they should have rooted. I did some about three weeks ago.