Julia here is what Erwin stated on his site about Sempervivum calcareum cf. ex LA BERNARDE PH1155
"We are not yet sure whether it is not a S. tectorum clone. The growth is not typical S. calcareum. We will wait for the flowering. However, we received it from a Sempervivum connoisseur. The boulder forms medium-sized rosettes with long drawn leaves. Overall an interesting form."
Cynda gets plants from Europe on occasion. This particular one is not verified as a calcareum yet. They are waiting to see blooms before making a decision.
Thank you for the link.
Alex, like anywhere else, research the seller. Easy to do here in our classifieds. Sellers are usually part of a community here on NGA.
Julia and I sell through the classifieds here at NGA. And Chris (goldfinch4) / Sempervivum Patch is also a member of our community.