Historical clue formulations

• Whack-___ — 2014-03-16
• Whac-___ (carnival game) — 2014-01-29
• Root used as a soap substitute — 2011-09-28
• Plant whose roots are used as detergent — 2010-12-10
• Whack-___ — 2010-09-22
• Whac-___ (carnival game) — 2009-01-31
• Soap plant — 2008-06-22
• Soap plant — 2002-12-22
• Agave root — 2001-04-29