Possible Clues:

• Unfading flower
• "There are no fields of –– on this side of the grave" (W. S. Landor, Imaginary Conversations)
• Long-lasting flowering plant often mentioned in poetry
• Love-lies-bleeding, for one
• A mother with diatribe on husband is a bloomer
• Plant has woman in nursery full of bombast
• ''Immortal'' bloom in ''Paradise Lost''
• Plant of the same genus as love-lies-bleeding
• Plant amazing initially, suffering harm when penetrated by insect
• No fade flower