Time to start uncovering rugosas in zone 4?
 

I planted a bunch of rugosas and hardy canadian explorers in July and
August of Last year and took special care to tent and mulch them for
the winter in case their roots hadn't established themselves. Now we
are in that zone of Spring-Winter where it can fluctuate between 15
and 50 degrees. Is it better to uncover them a bit so that they don't
get some kind of fungus and risk having them get nipped by a late
frost?

I'm in zone 4a, Minneapolis. Thanks!

mm