Here's a couple of pics of some of my calcareums:
Sempervivum calcareum 'Greenii' .................. Sempervivum calcareum 'Sir William Lawrence'
As you can see, 'Sir William Lawrence' is slightly more 'white' while 'Greenii' is more green. I think that 'Sir William Lawrence' also gets a bit larger than 'Greenii' but that is subjective. I have not measured them.
