They both may be dead. Zone 4 is pushing it for dianthus over winter unless planted in a very well drained soil and in lots of sun. And I am unaware of a lavender species or cultivar that will withstand a zone 4 winter. It also requires a very well drained, lean soil and lots of sun.

Both are generally considered to be evergreen or mostly so.

Yup. Both ex plants I'm afraid.

I've had lavender in zone 4 forever and mine is still dormant. I'd give it a bit more time before giving up on it. And yeah, you'll want to trim it back by like a half - at least that's what I do.

With the dianthus, maybe cut it back and see if there might be any signs of life underneath the dead stuff. Worth a shot anyway!

I’ve had dianthus for many years in my zone 3 and the foliage still looked fresh after winter. I would do what karin recommended. Cut it back and wait before pulling it out.