How is the sun there? All day, or when? Assuming enough sun=
Milkweed has several common cultivated species. The wild species syriaca will fill the entire area. Butterfly weed, a tuberosa, is a garden type that doesn't spread.
Beebalm, Monarda, is related to mint, will spread, and prone to mildew. The area looks a bit confined and maybe a mildew prone site.
Blackeyed susans- I think that garden types don't spread that much. Double check that
Coneflowers, would be great.
Bronze fennel- consider this as food source for some common swallowtail caterpillars. Not sure this is perennial or self sustaining though.
Whatever you plant, do mulch to keep it from growing up with weeds.
I look forward to others opinions on this
