Thinking out loud. Aren't series names also trade names and usually if not always trademarked? I'm not sure if this is an absolute but both Winter Thrillers and Under the Sea are trademarked. For the time being if we put the Series name in the Trade name field we'd have this:
Lenten Rose (Helleborus x hybridus Winter Thrillers™ Series = 'Red Racer')
Hellebore (Helleborus x hybridus Winter Thriller™ Red Racer)
Edit: doing research w/open response.
