That's a very nice, and a very large, flower Alain. I've grown S. borcherdsii, S. herrei, and S. pillansii, but never S. ruedebuschii. The ends of the leaves remind me of S. borcherdsii. These are great greenhouse plants as they like it hot and dry. You are showing a lot of nice plants. I'm sorry I haven't commented more but I have been looking at your wonderful photos. What is the size of your greenhouse?
I think the teeth make this less sculptural than some of the other Schwantesias and the old leaves do mark but I still find it attractive and the flowers are good. We had Derek Tribble talk to us at our last meeting. I am pleased you enjoy the photos. My greenhouse is 8.5 x 26 feet.