I'm just now seeing your response and pictures. I am SO sorry for the ultra late reply.
WOW, I LOVE your chickens!!! And man, you've got oodles of room to plant stuff!!

AND you basically have a clean slate. Sweeeeet!!
Let's see. I immediately thought of either a trumpet vine or a wisteria for a climber over the chicken fence. Both are very hardy, but can also be very invasive. :54: I don't think you'd have to worry about them being invasive though...not with all that room you've got. Trumpet Vine bears trumpet like RED flowers in the summer, and hummingbirds LOVE them! Wisteria bear long, purple flowers in the spring that smell heavenly.
PlantFiles: Detailed information on Trumpet Vine, Trumpet Creeper, Cow-Itch Vine Campsis radicans
PlantFiles: Detailed information on American Wisteria Wisteria frutescens
As for whites: There's the famous and heavenly scented Mock Orange. You could give the dwarf variety a try. Quite hardy and low maintenance.
Dwarf Snowflake Mock Orange - Monrovia - Dwarf Snowflake Mock Orange
Then there's the Hydrangea Paniculata. Also extremely low maintenance, and a long blooming period:
Hydrangea paniculata - PeeGee Hydrangea
Look for butterfly bushes. They, too, come in many different shades of colors and are super low maintenance and easy to care for.
https://www.mountainvalleygrowers.com/mvv2-94.htm
Rose Of Sharon (Hibiscus syriacus):
Rose Of Sharon Bush - Learn More About Growing Rose Of Sharon
If you like roses, but want think they are too high maintenance, look into "Knock Out" Roses. I swear, they're as low maintenance as you can imagine.
The Knock Out® Family of Roses | Star Roses & Plants
Daylilies! They come in all shapes, colors and sizes, come back year after year, and even multiply.
Daylilies: Frequently Asked Questions
You must know your gardening zone before you go out and purchase plants though!
Maine Interactive USDA Plant Hardiness Zone Map
The plants I listed are quite hardy, but I don't know if all of them are hardy enough to grow in Maine.