The RHS and ADS seem to cover cultivar registrations, but there are lots and lots of valid narcissus species out there that may not be covered by these two associations.
Check this out, for example:
http://www.theplantlist.org/tp...
I would consider any of those "Accepted" names to be valid.
But ultimately the db at ATP is not intended to be a dry academic resource. If there is a plant that hasn't been seen or grown for 250 years, I can't really see the main point of including it in the DB here.
