On a wet night slightly below zero, dead wood can be covered with white and silky threads. From a distance, one might believe a material deposited on the branch. These are ice hair.
Cold and water are not enough to explain their lasting form. Researchers have highlighted the role of a fungus, Exidiopsis effusa, present in the studied wood. Its activity helps the ice retain these very fine filaments rather than forming coarser crystals.
The branch thus offers a meeting between physical and living. What looks like a supernatural hair depends on a discrete organism, humidity and a narrow temperature range. The fungus is not necessarily visible; its participation becomes visible in the form of ice.
What we know
The fungus is involved in the formation and stabilization of the structure; the filaments observed are indeed ice.
To go to the source
References consulted on September 20, 2026. Linked pages may be in another language.
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