Historical clue formulations

• Tortoise's challenge to the hare — 2021-12-26
• Flower cluster whose name can also be read as a challenge — 2019-04-16
• Flower arrangement — 2017-04-30
• Flower-bearing shoot — 2015-05-02
• Flower cluster on a single stem, as in the honey locust — 2013-12-26
• Poinciana feature — 2010-11-06
• Flower arrangement — 2009-12-27
• Simple inflorescence, as in a lily of the valley — 2008-04-25
• Unbranched flower cluster — 1999-11-28
• Flower part — 1997-03-12