Saving Monarch Butterflies: Plant some milkweed, Asclepius
Milk weed is a attractive flower for rustic borders. It may not be the flower of choice for your formal garden, but there are plenty of places it could find home and not be a nuisance. People need to create islands of milkweed to allow the butterflies to make their migration.
You can order seed on Amazon. The Save The Monarch groups will send you seed if you send them a stamped envelope (although they would prefer you gave them a donation).