I recently read an article on heucherellas, written by an expert in them, and the related heuch/tiar. It said that heucherellas don't seem to thrive well in the NE USA, like they do in other locations, so that grower has stopped carrying them completely. Technically, Michigan (here) isn't the NE, but this has me concerned. Any comments?
Well I've found plenty of native heuchera and tiarella in the mountains of Eastern KY so I'd tend to think they'd do OK in your climate. The hybridized plants tend to be a little more fussy than the species in my experience. I've got natives of both plants that were nothing but tiny little plants just barely clinging to a sandstone bluff or boulder that are now 3 feet tall and 3-4 feet wide with huge leaves. Dan Heim among others have done some amazing things in the past 15 years but contrary to their claims that the Villosa hybrids are bred to handle heat much better, I still have lost several cultivars in the past 5 years mainly due to lack of heat resistance while the species have grown bigger each year. Hope this helps with your question!
ps: The heuchera americana is hybridized by some growers but the vast majority available east of the Mississippi River are villosa hybrids. My americana had leaves this spring that were 7-9 inches across! The only hybrid with leaves that shape and size that I have is Beaujolais and I believe that the Palace Purple is also an americana hybrid from the leaf shape.