Icy hair (Exidiopsis effusa) photo and description

Icy hair (Exidiopsis effusa)

  • Department: Basidiomycota (Basidiomycetes)
  • Subdivision: Agaricomycotina (Agaricomycetes)
  • Class: Agaricomycetes (Agaricomycetes)
  • Subclass: Auriculariomycetidae
  • Order: Auriculariales (Auriculariales)
  • Family: Auriculariaceae (Auriculariaceae)
  • Genus: Exidiopsis
  • Species: Exidiopsis effusa (Icy hair)

Synonyms :

  • Frosty beard

  • Ice wool
  • Thelephora effusa
  • Exidiopsis effusa
  • Sebacina effusa
  • Exidiopsis grisea var. effusa
  • Exidiopsis quercina
  • Sebacina quercina
  • Sebacina peritricha
  • Sebacina laccata

Exidiopsis effusa


Hair ice, ice wool or frost beard, also known as hair ice, ice wool or frost beard, is a type of ice that forms on dead wood and looks like fine, silky hair.

This phenomenon is observed mainly in the Northern Hemisphere, between the 45th and 50th parallels, in deciduous forests. However, even above the 60th parallel, this amazingly beautiful ice can come across almost at every step, if there was only a suitable forest and "correct" weather (author's note).

Exidiopsis effusa

"Ice hair" is formed on damp rotting wood (dead logs and twigs of various sizes) at a temperature slightly below zero and a fairly high humidity. They grow precisely on wood, not on the surface of the bark, and can appear in the same place for several years in a row. Each individual hair has a diameter of about 0.02 mm and can grow up to 20 cm long (although more modest specimens are more often found, up to 5 cm long). The hairs are very fragile, but, nevertheless, they can curl into "waves" and "curls". They are able to maintain their shape for many hours, or even days. This suggests that something is preventing ice recrystallization - the process of turning small ice crystals into large ones, which is normally very active at temperatures just below zero.

Exidiopsis effusa

This amazing phenomenon was first described in 1918 by the German geophysicist and meteorologist, the creator of the theory of continental drift, Alfred Wegener. He suggested that some kind of mushroom might be the cause. In 2015, German and Swiss scientists proved that this fungus is Exidiopsis effusa, a member of the Auriculariaceae family. Exactly how the fungus causes ice to crystallize in this way is not entirely clear, but it is assumed that it produces some kind of recrystallization inhibitor, similar in its action to antifreeze proteins. Anyway, this fungus was present in all wood samples on which "ice hair" grew, and in half of the cases it was the only species found, and its suppression by fungicides or exposure to high temperature resulted in the "ice hair" not appearing anymore.

Exidiopsis effusa

The mushroom itself is rather inconspicuous, and if not for the bizarre hairs of ice, they would not have paid attention to it. However, in the warm season it is not noticed.

Exidiopsis effusa

Photo: Gulnara, maria_g, Wikipedia.