Quiet Crust
Lecanora liminis
A grey doorstep lichen from Mansourah that keeps a circle of perfect silence around itself, 2 mm wider every year.
Unheard-Hour Hortênsia
Hydrangea macrophylla
Walk the full 31 metres of this Penzance hydrangea hedge and no one can hear you for an hour, as a neighbour did at two in the morning in March 1971.
Threshold Oboe-Cane
Arundo donax
An oboe reed cut from Vukovar cane is silent except in doorways, and its maker listed 37 of them and sealed a 38th in a footnote.
Third-below Coelogyne
Coelogyne subtertia
Lisu children raised under one Fugong chestnut can sing only a third below another voice; alone they make no note, and neither does the dog.