I am thinking the real threat to saucer magnolia in winter is the wind, so really the location is the crucial thing. But if you do want to mulch, you could try bark or leaves and see if that holds less moisture.

If your magnolia is hardy to zone 5 and that's the zone where you live, you shouldn't have to do ANYTHING for it. I've read that siting Magnolias (that flower before setting leaves) in protected sites only MAGNIFIES the chance they'll be nipped by late freezes. Plants have an uncanny ability to adapt to their site. Pamper them too much and you'll get a plant that "folds" when the going gets tough... site it properly and it will take care of itself.

We have a Magnolia stellata. It's been here for 12 years now. It's sited the direct path of the northeast wind. And NEVER has it failed to flower or grow! It's 8' x 8' now and thriving.

When siting a rhody this past summer, all the reading told me it's the south wind that's the harshest.

Wow, that's really interesting! My Saucer Magnolia is living against all odds...it's planted on the north side of my house, and away from any shelter or protection. Maybe it will do fine with 'tough love.'