An interesting article on GardenRant on the history of the US nursery Wayside Gardens and others (Park Seed, Bluestone Perennials, Bentley Nursery, Antioch Farm and Beardslee Nursery):
http://gardenrant.com/2017/11/perennial-royalty-its-inbred.html
http://gardenrant.com/2017/11/perennial-royalty-its-inbred.html