Small but dense flower heads.  The sterile florets are entire slightly dished sepals.   They are pink on alkaline soils but a beautiful sky blue on acid soils.

Gardens found in 28 pre 2000 surveys DA  LHS WIN TR WS RW ABJ

Gardens found in the 10 surveyed in 2010: DA LHS ESV ABG NAN AW

UK  Plant Finder 2012 = 1 nursery