The forest was growing hair (and then it vanished)

Hair Ice Mycelium❄️🍄

In late December 2025, while walking through our neighbourhood parks in the early morning (right at dawn), we stumbled across something I had never seen before, and it stopped me in my tracks.

After weeks of storm activity, the forest floor was littered with fallen branches, especially cottonwood. But one branch looked… strange. It had split along the stem, and from inside it was “spewing” this white, silky material; almost like someone had sprayed silly string into the woods.

Taken: January 2026, Pacific Northwest, USA

Except… it wasn’t string.And it wasn’t fluff.And it definitely wasn’t cottonwood seed.

It was something else entirely.

This strange white “hair” was emerging from multiple pieces of dead wood all around us. It looked soft and silky, but when touched it wasn’t quite hair-like. It felt rubbery and oddly structured, like delicate fibres holding their shape.

It was incredibly weird...and cool...and of course I forgot my phone.

And then… life happened. We got home, thought I should go back, got distracted, and I forgot about it until a few days later when curiosity returned and I went searching for what on earth we’d seen. But, in less than 48 hrs, it was gone.

Turns out: we had witnessed one of the most magical winter phenomena in the forest.

What we found was: Hair Ice (aka “frost beard” or “ice wool”)❄️

Hair ice is a fragile, hair-like ice formation that grows on moist, rotting broadleaf wood, often overnight when conditions are just right.

It looks like cotton candy.

It behaves like silky fibres.

But it’s actually ice shaped into hair-thin strands.

And the best part?

It’s not just weather.

The secret ingredient is a fungus🍄

Hair ice is strongly associated with a winter-active fungus called Exidiopsis effusa, which lives inside decaying wood. Research has shown that this fungus helps shape the water into ultra-fine strands and stabilizes them by suppressing recrystallization (which would normally cause the ice to clump and collapse).

This is a stunning example of fungi quietly doing what fungi do best:

✅ transforming dead material

✅ building hidden networks

✅ shaping ecosystems

✅ and (apparently) sculpting ice into silk

How it forms (the simple version)🧊

Hair ice appears when:

• the wood is moist and decaying

• the night is humid

• temperatures hover just below freezing

• and the wood itself is not fully frozen

Water migrates through the pores of the wood and freezes at the surface, forming those delicate “hairs” through a process called ice segregation.

And then it disappears✨

Two days later, when we went back, the hair ice was completely gone.

That’s one of the reasons this phenomenon is so rarely noticed: it’s brief, fragile, and disappears quickly with slight warming, wind, or sunlight.

A tiny reminder🌎

Moments like this make me love forests even more.

Even when the ground looks messy, broken branches, storm debris, fallen wood, the ecosystem is working. Fungi are connecting, transforming, and literally reshaping the world in ways we don’t usually see.

And sometimes… they leave behind something that looks like snow-white hair spun from magic.

P.S. A month later in January, on another chilly morning walk, it showed up again! This time I had my phone.