I live in Zone 3A and have a mixed rose border with lots of bulbs in it. I
applied a heavy mulch of leaves over my bulbs a good while after freeze-up.
This is the third year I do this mulching.

Now I looked under and lots of Muscari are poking up. Oh dear. There must
have been more heat still trapped in there than I thought.

What's odd is I thought this growth could not happen without a good hard
cold dormancy period. My tulips, narcissi and everything else are not
coming up. I certainly can't save the muscari from the rest of winter. So
I just put the leaves back.