I have 3 or maybe 4 Heuchera's that survived our crazy winter and spring, but I do
know what I did to have them do so.
They are in containers one of which is a plastic pot the other is a foam Urn. I used MG with a little gravel added.
I am still not clear on the water requirements of these plants
If you have a good link on a "How to Grow Heucheras" it would be appreciated.