Thalictrum 'Delavayi' 96 of 100 must have garden plants, 'chosen by people like Dan Pearson, Piet Oudolf, Fergus Garrett and others..." http://www.juniperhillfarmnh.com/2011/03/100-must-have-garden-plants.html
MJM Garden Design, Janie McCabe - Consultation & Design for a New Garden
Aliums with Alchemelia Mollis, two of my favourites. For the right hand border in the ECG?
Verbena and Cosmos. Verbena bonariensis, flowering season August-October. Likes the sun.
Flax - one hearty plant that come up year after year - and the deer won't eat it!