Historical clue formulations

• Trees in the birch family — 2024-02-29
• Non-conifers that bear "cones" — 2023-09-07
• Birch relatives — 2020-06-30
• Hazel relatives — 2016-02-19
• Charcoal wood sources — 2009-05-29
• Catkin bearers — 2006-07-23
• Birch relatives — 2006-07-11
• Birch family trees — 2004-05-12
• Charcoal wood sources — 2002-04-13
• Trees with catkins — 1997-12-30
• Members of the birch family — 1997-05-17
• Thicket trees — 1995-11-12
• Drug-yielding plants — 1995-09-29
• Birch-family trees — 1994-06-19