Esther, I think the frost-free date pertains more to annuals than perennials. I think your heuchera will be fine exposed as it is winter hardy. Mine is but one opinion. :-)

Thanks, Josephine. I was more worried about the pot and the freeze/thaw cycle causing it to crack than the heuchie. I have about 10 heuchies of various varieties in the ground, and they are showing teensy signs of new green. I just hope their bits of green don't get knocked down by frosts we are scheduled for the latter part of this week. I have another pot of mini hostas still covered to avoid the pot cracking, and a third pot with one single hosta, also still covered.