Some suggestions:
Eupatorium perfoliatum
eupatorium rugosum
parthenium integrifolium

As with any most prairie plants, they may not bloom in their first growing season.

hiya, a bit late i know but: orlaya grandiflora, ammi visnagu (my spellings are a bit dodgy and not always sure of latin), chaerophyllum roseum, sellinum, wild carrot (dauca something)anthriscus sylvestris 'Ravenswing' - all easy umbellifers but not all perennial. I have a white meadow which is mainly oxeye daisies and cow parsley but have planted other umbelliferas and also gladioli 'the bride, cammasias anthemis cupiana,larkspur and cosmos bipinnatus 'Purity'- i think it is gorgeous but is high maintenance since there is a lot of deadheading and i usually have to sort out the faded oxeye daisies.

Amni majus.