"My guess is that moonflower is perennial in Michigan and I would like
to hear from
people who have them."
Moonflower is definitely not a perennial in Michigan. I'm in central
Ohio, which is a zone or two warmer than where you are, and they are
not perennial here. Morning glories (same family) weren't even a
perennial for me when I lived in South Carolina, although they did
reseed like crazy.
Hope for seeds and collect them. Put them in a jar in the fridge and
start them outside (not inside, because most of them won't survive
repotting) after the last frost. Soak them in warm water the night
before you plant them and you'll have a good result.