Historical clue formulations

• "Immortal" flower in "Paradise Lost" — 2016-01-14
• Flower that symbolizes immortality — 2015-07-19
• Undying flower — 2007-04-08
• Imaginary undying flower — 2005-07-20
• Unfading flower — 1998-12-25
• Imaginary, undying flower — 1998-07-25
• Love-lies-bleeding, for one — 1994-09-06