Answer: Unfortunately, I checked and Tuscan Blue is only hardy to zone 8, or 10 to 20 degrees and your zip code places you in the coldest part of zone 7. That, combined with a northern exposure in the winter and possibly a less well drained site would probably account for losing them. (Snow is actually a good insulator so snow alone is not to blame.) You might have two different varieties, possibly something a bit hardier such as Arp or Hill Hardy, which might help explain why they look so different as well. I'm really sorry about your plants but I do think you were lucky to keep the going as well as you have. They do best in a sunny site with protection from winter winds and also perfect drainage, for this plant winter wet is as damaging as the excessive cold. I hope this helps.
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