Some of us are pushing the limits of southern magnolias and growing them in
Spokane Washington zone 5/6. (Varieties Edith Bogue and Poconos). So far so
good. (I know of some here that have survived at least 10 years). The
species itself is native only to the southeast - basically zones 7-9, and
probably most "comfortable" in z. 8-9. I think probably they were first
found only along the seacoast from Norfolk Va south, and more and more
inland the further south one goes, so that they were very common throughout
central and south Georgia, Florida, Alabama, Mississippi, and Louisiana.
However, for their great beauty of foliage and flower now they are grown up
the east coast as far as Boston, throughout California, the coastal areas of
Washington and Oregon, throughout much of southern and western Europe, and I
imagine, even in Japan and China. The cold damage problems we see in spokane
are leaves that are damaged or killed by cold dry winds in winter when the
ground is frozen, and sometimes snow damage (broken limbs and stalks).