Time for a discussion on S. 'Rubrum'.
We seem to have more than one type showing in the database. In just a few minutes of research I see there are more than one semp sold under this name.
Every one put your sleuth hats on and see what you come up with.

This may be part of the problem. http://garden.org/plants/searc...

This is my rubrum. It says arachnoidum var. rubrum. It's not the best right now. It's still semi dormant and needs to be cleaned up, but here it is.

Lynn, I think the term 'Rubrum' has been used for several things. In my youth it was the reddish form of montanum, that was probably one of the parents of of 'Cleveland Morgan'. Probably a cultivar name that simply means RED is not a good one in a group of plants where we have several thousand that could be called that.

Kevin

And it's very tiny isn't it Margo? Looks like mine. And I think Dirt has the same one.

We cross posted Kevin. I see what you mean, there are several going by that name.
I find this tiny one is being sold by:
Mountain Crest http://mountaincrestgardens.co...
SMG http://www.smgsucculents.com/s...
Monrovia http://www.monrovia.com/plant-...
Wrightman Alpine Nursery https://www.wrightmanalpines.c... https://www.wrightmanalpines.c...

Nargs has it featured: https://www.nargs.org/photo/se...

I also have found French sites that show this same tiny arach. They all look to be the same plant with the same name at different times of the year.

and frankly none of those seem any more red (in fact much less red) than 'Emberly Pink'.

Kevin

Yes, it is tiny, Lynn. That's another one that's about 1/2" full grown.

Great discussion
Here are 2 that I have
first one is labeled Sempervivum arachnoideum rubrum...just like nargs picture...which I have always thought was a species because of the small r in rubrum. Perhaps it should be subspecies rubrum
The second one is just sempervivum Rubrum as if Rubrum is a cultivar name. I have no idea how long this variety has been around. As Kevin says ..there are so many red ones now that the name seems almost silly but maybe it is very old. Does it look like anything you remember Kevin ?

There is another one that is a montanum too. That was the one from my youth. I'm sure it was involved in 'Cleveland Morgan' as it was like a smaller less red version of CM.

Kevin

Nice photos Jo Ann.

Thanks Lynn. That's my now famous camera
Kevin, my Cleveland Morgan is not as red as either of these. Breeding has vastly improved color hasn't it. I saw a few beautiful lime and chartruse semps in your beds. do yoou think that breeding for those colors is a worth while project. Perhaps I am off topic here and this is not appropriate discussion for this thread. ?

Jo Anne, you can start a new thread anytime you want to start a new topic concerning semps.
Use the Search box on the home page of the Sempervivum Forum to see if the topic has already been discussed, if not just start a new topic.
Your above post would be a great topic to pursue.