Magnolia sieboldii 'Harold Epstein'
This is a semi-double flowering form of M. sieboldii which probably originated as a seedling purchased by Harold Epstein. The original plant is over 50 years old. He also reported that in his garden the plant flowered in the fall with fully-double flowers rather than the semi-double flowers which appeared the earlier spring. 'Harold Epstein' should be hardy to zone 5.