Intuitive and simple is always best.
Your talking about the "advanced" Rose search aren't you Sue? My comment was about the "standard search". The advanced search already does this. Check Siberian or Tall Bearded and voila!
1. If a script could fill in "Siberian Iris" as a secondary common name for all entries that have -Classification: Siberian- that's great. Sounds like you could do the same for all of the Iris classifications. Some have several entries under Classification, usually the -Interspecies Hybrids---Species X-
2. Can a script also add "Siberian Iris" as a secondary common name for all entries that have sibirica as species? That will take care of most of the siberians. Can a script then delete sibirica from the species field for all of these? I can then recreate -Iris sibirica- which is a single entry.