I’m not from the mid Atlantic but I have tons of plants in my chicken run that flourish. My run is 25’x58’ with 12 chickens as of now (20 come early summer). The key with plants in the chicken run is to choose hardy plants that get large. I protect the roots of each plant with large rocks that the chickens can’t kick away. Any new plants I add are protected with a wire cage for a few months until it has a noticeable amount of growth and is about 2’ taller than the chickens are. You also want to pack in as many plants as you can fit. 2 lone plants won’t stand a chance against chickens but if you have 20+ then they’ll do a lot better. I stick with hardy shrubs and fruit trees. I grow berries and grapes along on the outside of my run, it’s used as a trellis.
Some plants that have done really well in my run are; Native plants, plants in the sage family (I have hummingbird sage, compact Texas sage, Mexican bush sage, and big sagebrush), bushing rosemary, English lavender, fruit trees, butterfly bush, and surprisingly marigolds (I had about 20 in the run that just died at the first frost). I have multiples of a lot of these plants. I’m planning to add a lot more plants this spring. I’m going to try some more natives, fruit trees, and climbing roses. My entire run is also a deep litter compost system so that keeps the chickens very entertained and they really don’t mess with the plants much at all.