Hair Ice and Frost Flowers: Beautiful Ice Crystal Structures

Hair ice can grow from logs in the ground and sometimes looks like a silky beard. Photo: Tricia Edgar

Hair ice can grow from logs in the ground and sometimes looks like a silky beard. Image courtesy of Tricia Edgar, all rights reserved.

Natural frozen formations, hair ice and frost flowers, may form in your area during the winter.

What are those spidery, silky threads growing on that log? What’s that ghostly flower pushing its way out of the ground? Is it a fungus or a piece of fabric?

Winter creates some wonderful ice formations, and the natural phenomena known as frost flowers and hair ice are two of the most intriguing.

Frost Flowers and Hair Ice Aren’t Made From Frost

If you’re walking along in the forest and you see something icy on the ground, your thoughts may turn to the more traditional water formations: ice, snow, and frost. Frost flowers and silky hair ice aren’t actually made from frost, however.

Frost occurs when airborne moisture lands on the ground or on plants, covering it with a white coating of ice.
Frost flowers and hair ice are actually ice crystal formations that come up from the ground. This is why they look like they are growing.

Carbon dioxide made by fungi pushes filaments of ice from the logs. Photo: Tricia Edgar

Carbon dioxide made by fungi pushes filaments of ice from the logs. Image courtesy of Tricia Edgar, all rights reserved.

Silky Hair Ice Grows on Cold, Wet Logs

When you walk in the forest in the Pacific Northwest of North America or in Western Europe, you may see strange, cotton candy-like formations on the logs in the winter time. This is hair ice, and it looks just like tiny, silky hairs.

How does hair ice form? When it rains, logs are the perfect material for soaking up moisture. Their rotting, spongy interiors fill up with water, so much so that if you squeeze them, water comes out as it would from a sponge. When the water freezes, it expands out from the pores in the frozen wood, creating fine threads of ice. The “hairs” of ice can be quite distinct from each other.

In studies of hair ice formation on beech wood, it appears that the presence of fungi in the wood also helps push the ice through those little pores. Some fungi are active in logs in the winter time. These fungi produce carbon dioxide and water as products of their activity, and the carbon dioxide helps push water out through the pores in the wood. Beech logs treated with antifungal agents do not produce as much hair ice.

Frost flowers grow from plant stems that crack open. Photo: US Department of Agriculture / CC by 2.0

Frost flowers grow from plant stems that crack open. Photo courtesy of the US Department of Agriculture

Beautiful Frost Flowers Grow In the Winter

Frost flowers appear to grow from the ground, and as the day warms they often melt. Like hair ice, these beautiful, thin clusters of ice grow from wet places, but for the frost flowers, these wet places are the insides of a plant.

Frost flowers form in part due to the difference between ground and air temperatures. On winter days when the ground is still warm enough for a plant’s roots to keep it alive but the air is cold enough to freeze, the plant continues to move water up from the roots.

As the water moves into the plant, it is now surrounded by the cooler air temperature, and it begins to form ice crystals. Since water expands as it freezes, these expanding crystals split the plant stem open as they “grow”.

This phenomenon occurs mostly in thin-stemmed, annual plants. Each frost flower is unique, since the plants’ stems split in different ways each time the frost forms. This leads to swirling, ephemeral designs made in ice.

Finding Frost Flowers and Hair Ice

Frost flowers and hair ice only last for a short time. If you’re looking for examples of these natural ice sculptures, wait until your area experiences damp days followed by a freeze. Frost flowers are best found in areas with abundant thin-stemmed plants, such as Verbesina virginica, which is also called frostweed. Look for these tiny ice structures first thing in the morning before the sun touches them, as they will disappear as the day warms.

© Copyright 2014 Tricia Edgar, All rights Reserved. Written For: Decoded Science

Resources for this article

Carter, James R.. Ice Formations on Dead Wood – Haareis or Hair Ice. . Illinois State University. Accessed on January 08, 2014

Gerhart , Wagner . Hair Ice of Rotten Wood of Broadleaf Trees -- A Biophysical Phenomenon.. (2008). Bern University Institute of Applied Physics. Accessed on January 08, 2014

Texas Parks and Wildlife. Frost Flowers. Accessed on January 08, 2014

Washington University in Saint Louis. Frost Flowers Will Bloom Soon. Accessed on January 08, 2014

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