I am thinking of a trip to Whately Mass. to see the New England Wildflower Society plant propagation farm.

....(It) opens its 2009 Spring Season Thursday, April 16 and will remain open Thursdays through Sundays until June 14. The Society’s nursery propagates and features over 450 native plant species for sale

They have quite a number of New England plants for sale there, and their website provides a list with prices