There is only one species in the Calluna genus. C. vulgaris is native to Europe including the Azores Islands west of Spain, the British Isles, the Faroe Islands and Iceland. This species used to be combined with the genus Erica, but Calluna has only 4 parts to its corolla and calyx instead of 5. Erica species are also referred to as heathers or heaths, and there are several other genera. THE HEATHER SOCIETY may provide you with more info on hardy cultivars.

I am not as cold as you are since we get to between -20 and -25F in our coldest winters, but I imagine that otherwise our growing conditions are similar. I chose all my varieties as cultivars that remain short so that snow would provide the needed insulation. I don’t know if your part of the UP reliably gets a good amount of lake effect snow, but if it does, that will be your best insulation, keeping temperatures under the snow not too far below 32F regardless of air temperatures, and will prevent drying out or winter burn of the foliage. I chose types that would stay below 1’ since that mostly allows them protection from the worst of the cold. Any mulch should either be on the ground under the branches or very loose and airy since these are evergreen plants and like other evergreens aren’t adapted to be in the dark all winter.

I don’t remember any names since most of my heathers were at a previous residence. I will look for tags on the few I have here. My previous source closed, so I buy them now as I see them locally, but they aren’t commonly available.

None of the species in the genera Erica or Daboecia (common name heath) have any chance of survival for you since ethey aren’t reliably hardy here.

The link above to the Heather Society doesn’t have any hardiness info, so not much help for your questions about hardiness.

The link below is the best online source that I know of in the US, but they also don’t give hardiness info. They have a ton of varieties and give height and width info, so you can choose shorter ones that will stay beneath the snow for the winter.

http://www.heathsandheathers.com/cart1/HHWebCart12010_Page421.htm

I think that since you are zone pushing for heathers, it will largely be a matter of trial and error for you and your particular garden. If you have spots that are sunny during the growing season when the sun angle is higher but get shade in winter when the sun angle is low, that may be a good choice for you since the snow is most likely to remain in those spots for insulation and are less likely to melt and refreeze. If you have areas that the snow consistently drifts onto from wind, those would also work well, but avoid spots where snow is piled from shoveling, snow plowing, dumping from the roof, or snow blowing since that tends to be much denser and can damage the woody branches of the heather.

I would enjoy updates as your heathers grow.

Thanks NHBabs. I hadn't heard the recommendation of not burying the plants completely. I've been covering all with coarse sawdust and/or pine needles. We are inbetween on snow volume and usually have enough but with the changing climate it's more iffy now. My heathers are in my orchard and in a safe snow area. We only have a maybe 4-6" as yet so I may uncover them (having a mild spell right now), moving the sawdust off and covering instead with pine boughs (if the sawdust isn't frozen). I've purchased my plants from Fedco; they offer a few different varieties each year, all short and hardy. But I thought I might check out some others. Thanks for your comments. I'll report back on how my plants do. Sue

Pine boughs would be a great choice.

Or even pine needles.