I remember seeing these in bloom in the Chinese garden at the Missouri Botanical Garden in St Louis. They seem to be hardy there, but they were right next to a pavilion, and maybe they get a deep winter mulch.
we live on the west side of Missouri and get completly different weather than St. Louis. We grew them outdoors at the beginning and mulched heavy on the southwest corner of the house. they did not do well. We are right on the hardyness line of where you can grow them. we are zone 5b and I think striata is zone 6. it seems to work best for us to grow them this way.