When Wood Grew Hair
Category: The Unclassifiable 14th June 2026
Oddly, some dead twigs grow hair. Not the sort you tidy with scissors, but filaments of ice so fine and feathery they look like a miniature powdered wig dropped by a very polite ghost. Walk through a damp, beechy wood on a calm night just below freezing and you might meet them: hair ice, also called "frost beard" or Eiswolle, clinging to rotting broadleaf wood in clouds of white.
How do sticks sprout coiffures? It is not witchcraft, and it is not the work of a disgruntled hedgehog. The show needs three things: rotting hardwood, air temperatures slightly below zero, and a particular fungus. Scientists have found that wood bearing the fungus Exidiopsis effusa reliably produces these silk-thin ice strands. Remove the fungus and the hair does not form; leave it be and physics does the rest.
Water in the pores of the dead wood is pushed out through tiny channels as freezing begins. Instead of forming one solid block of ice, the liquid extrudes as very thin filaments that freeze immediately on contact with the air. The fungus plays the cunning role of midwife: it appears to regulate the crystal growth, probably by secreting organic compounds that stop the ice from recrystallising into larger, boring lumps. The result is tens of thousands of hairs, each a fraction as wide as a human hair, sometimes several centimetres long, holding their shape for hours on still, humid mornings.
They are delicate, ephemeral sculptures. A puff of wind, a ray of sun, or a clumsy boot will demote the twig from haute couture to soggy twig in a heartbeat. For a brief, absurd instant, the forest displays something neither plant nor animal, where biology and thermodynamics conspire to make winter behave like an eccentric milliner.
If you like the idea of nature pulling off a neat, implausible trick while the rest of the world does the sensible thing and stays ordinary, hair ice is peak oddity. It is quiet, elegant, and perfectly useless-exactly the sort of ridiculous miracle I approve of.