Pacific Northwest
Washington State.
Whatcom County woodlands
Although not really rare, “hair ice” or “wool ice”, is not often seen. It occurs under fairly specific circumstances such as temperature, moisture, the substrate on which it will grow, and the presence of a specific fungus. I ran across these interesting phenomena on several of my recent forest excursions. At the time I was looking for mycelia and fungi. When I first saw this fuzzy sight, I thought it was a variant of fungal mycelia with which I was unfamiliar as it was so strikingly different. Some of these odd structures turned out to be mycelia and others were mycelia-related. I’ll explain shortly.
Although hair ice has been described and theorized about in the scientific literature for over 100 years the research has been minimal and the exact mechanisms by which the hairy strands form is not totally clear. The first scientist in modern times to describe it was Alfred Wegener, a German arctic meteorologist who described hair ice in 1918 and suggested that a fungus was implicated in its formation. (Wegener, a keen observer was also the first in the modern era to postulate the theory of continental drift that became the basis for tectonic plate theory). Wow!
So, What the Hell is Hair Ice?
First, hair ice is indeed ice as from frozen water. Instead of growing sheets of crystals, the frozen water forms these minute hair-like structures that curl and wave (~ .01 — .02 mm dia.). And it does not occur just any old time that there is water and freezing temperatures. It is very picky as to how, when and where it freezes this way. The conditions are as follows:
- Temperature is just below freezing,
- The air is moist (water vapor) and calm (otherwise it sublimates quickly)
- It only grows on dead twigs and branches of broad-leaf trees.
- Those branches must be devoid of bark or if bark is present it is loose and flaking from the limb so the underlying wood surface is exposed,
- These branches must be infiltrated with mycelia of the winter active fungus, Exidiopsis effusa,
- It is located typically between latitudes of 45 and 55 N.
- It is not found on the ground, leaves, or on living trees where frost might typically be found.
I have seen these oddities now on two occasions since my first observation just these past couple of months. I might well have seen these before but did not know what I was observing. They are not seen as often as one might expect since it typically forms at night as temperatures drop to freezing and it melts in the morning as temps rise with first sunlight.
Also, if there is snow around or ground frost, the hair ice does not stick out. However, if there had been a light freeze without frost or snow, its prominent but spotty nature sticks out.
The main research into these processes has been conducted by a team of scientists in Germany and Switzerland whose work has substantiated the process described as follows:
“... the driving mechanism responsible for producing ice filaments at the wood surface is ice segregation. Liquid water near the branch surface freezes in contact with the cold air, creating an ice front and ‘sandwiching’ a thin water film between this ice and the wood pores. Suction resulting from repelling intermolecular forces acting at this ‘wood–water–ice sandwich’ then gets the water inside the wood pores to move towards the ice front, where it freezes and adds to the existing ice. “Since the freezing front is situated at the mouth of the wood rays, the shape of the growing ice is determined by the wood rays at their mouth,”
Apparently the light freeze is just cold enough to form ice at the surface of the wood but not so cold as to freeze the water inside the wood pores. Akin to the “frost heave” phenomenon.
Further, they now believe that the role of the fungus is that it contains traces of particles that serve as an anti-freeze at the surface, keeping the water from freezing and growing into larger ice crystals. When they deactivated the fungus through either boiling the wood or use a fungicide on it before testing, the water froze as is typical into a crust-like structure on the surface of the wood.
Note the fruiting body is a patch of unremarkable thin whitish coating stuff.
Without the Ee, the same twigs produced a crusty ice patch.
Previous to finding and identified this most interesting ice, I had come across something else at one of the woods where I walk. It first struck me as shaggy dog hair as if someone had brushed their dog and just left the grey-white hair along side of the trail. Then I saw it several places as I walked that morning and decided that if it were dog hair, the dog would be bald by then.
Only after having discovered hair ice a couple of months later did it dawn on me that this might have been a version of hair ice. Fortunately, I had taken a photo of it, but not knowing what it was, I did not check it out further at the time.
Searching back through my photos, I found it and submitted it to Seek to see what it was. Seek immediately recognized this as a fungus of the genus Phycomyces but was unable to recommend a species. I subsequently IDed it to be blakesleeanus. So, mystery solved — it was a new species of fungus for me.
What kinds of oddities are you finding in your backyards these days?
