Q.Verbena Bonariensis
I planted 2 Verbena bonariensis plants last year. They were mature plants and grew well and produced beautifully. I did not overwinter them- leaving them in the ground. I cut them back to approx. 4″ I live in southern Maine, Zone 5a/5b. It is now late May and the two plants appear brown, with no sign of greenery. Should I dig them up and move them? Did I kill them? I’m devastated!

Certified GKH Gardening Expert
It is not your fault; they are not hardy in your area so what you planted last year won't come back. The good news is they usually reseed. You may see a few pop up later as it continues to warm. Here is more about their care:
https://www.gardeningknowhow.com/ornamental/flowers/verbena/grow-verbena-bonariensis.htm