Lynn, I think I understand what you'd like to do: Find all Sempervivum that have a species, with or without a cultivar name. So Sempervivum marmoreum would show up with Sempervivum marmoreum from Kanzan Gorge, S. m. 'Brunneifolium', S. m. var. dinaricum, etc. even though the cultivars are mixed in with the hybrids.
If that's correct, it's not possible to do now without a special "Dave search".
When you queried for Sempervivum species, the system actually looked for the word "species" and didn't find one. That's why you got no return on your search investment
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