Historical clue formulations

• Flowering period — 2026-07-18
• Nursery sight — 2025-04-20
• What fire poppies do after a wildfire — 2020-09-09
• Sign of spring — 2017-04-09
• Boutonniere part — 2016-06-14
• Leopold ___, "Ulysses" protagonist — 2015-12-29
• Begin to flower — 2015-11-30
• What century plants do only once — 2014-07-30
• Come to fruition — 2012-09-04
• A flower is pretty when it's in this — 2011-09-08
• Burst into flower — 2010-12-21
• Flower — 2009-10-27
• 48-Across's partner — 2007-04-19
• Bud, in time — 2006-03-22
• Flourish — 2005-02-11
• Flower — 2001-02-19
• Rose's beauty — 1999-07-05
• Blossom — 1999-03-22
• Gardener's pride — 1998-05-06
• Rarity for a century plant — 1998-02-24
• Flowerage — 1994-11-19