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A frost flower is a name commonly given to a condition in which thin layers of ice are extruded from long-stemmed plants in autumn or early winter. The thin layers of ice are often formed into exquisite patterns that curl into "petals" that resemble flowers.
There are two types of features in nature that are called Frost Flowers.
One type of Frost Flower is the growth of frost crystals on frozen surfaces. Most of these have been observed on ocean surfaces in the Arctic and Antarctic but have also been observed on lakes and over land. In this form the underlying surface is frozen. There seems to be no alternative name for this type of ice formation.
The other type of Frost Flower is the growth of ice on plant stems by the process of ice segregation. This occurs only on a few variety of plants when the air is below freezing but the soil is still above freezing. In this process supercooled water moves through the plant stem to the surface where it freezes. As the process continues the addition of ice at the stem pushes the existing ice out to create a great variety of ice forms.
There has been some confusion in the use of the name Frost Flower and in at least two occasions an explanation for the formation of Frost Flowers has been applied to the inappropriate form of ice.
There is no standard name for the ice formations on plant stems. It has been proposed to use Ice Flowers and Crystallofolia, but one may see descriptive terms such as "ice ribbons", frost castles, ice castles, ice blossoms, and "rabbit ice".
The process of ice segregation that produces Ice Flowers also produces Hair Ice on some pieces of dead wood, Needle Ice on some soils, and Pebble Ice on some small rocks.
Types of frost flowers include needle ice, frost pillars or frost columns, extruded from pores in the soil, and ice ribbons, rabbit frost or rabbit ice, extruded from linear fissures in plant stems. While the term ice flower is also used as synonym to ice ribbons, it may be used to describe the unrelated phenomenon of window frost as well.
Hair ice, frost beard, ice wool, or feather frost describe a hairy, sometimes silky variant of frost flowers, extruded from openings of histological rays in the wood, which also requires the presence of fungus metabolism.
The formation of these two types of ice is very different. The only thing in common is that the air temperature at the site of the formation of the ice is below freezing.
The formation of frost flowers on plant stems is dependent on a freezing weather condition occurring when the ground is not already frozen. This type of ice formation does not occur because of the expansion of water when it freezes. If and when water freezes and expands in the plant stem, the stem ruptures or shatters, and this does occur.
The process of the formation of ice flowers is called ice segregation and has been demonstrated in controlled lab experiments. It involves supercooled water moving to an ice surface, freezing and pushing the existing ice out. As such it can continue as long as there is a supply of water, it does not get too warm, or does not get too cold and everything freezes up. As this process takes place latent heat of fusion (freezing) is added to the process which counters the cooling.
There are very few plants that support the growth of ice flowers through ice segregation. Ice segregation occurs as Needle Ice in some soils such as clayey silts. A variation of Needle Ice is Pebble Ice where ice grows on individual small rocks of pieces of brick. Hair Ice grows on pieces of dead wood where there is no bark. Only a few species of wood exhibit this property and it has been shown the presence of a fungus is a necessary factor. In all of these cases the size of the pores is an important factor.
The petals of frost flowers are very delicate and will break when touched. They usually melt or sublimate when exposed to sunlight and are usually visible in the early morning or in shaded areas.
Examples of plants that often form frost flowers are White Crownbeard (''Verbesina virginica''), commonly called frostweed, yellow ironweed (''Verbesina alternifolia''), Dittany "Cunila origanoides" and Frostweed ''Helianthemum canadense''. There is considerable doubt that Yellow Ironweed supports the growth of ice flowers.
Hair Ice or Haareis in German was written about by the later half of the 19th Century. The meteorologist and discoverer of continental drift Alfred Wegener, described hair ice on wet dead wood in 1918, assuming some specific fungi as catalysator, a theory mostly confirmed by Gerhart Wagner and Christian Mätzler in 2005.
Arctic "sea meadows"
||It has been suggested that this section be merged into Frost flower (sea ice). (Discuss) Proposed since November 2013.|
On Sept. 2, 2009, a University of Washington biology team sailing back from the North Pole encountered these little flowery things growing on the frozen sea "like a meadow spreading off in all directions. Every available surface was covered with them." When allowed to melt, the one to two milliliters of water recovered was found to hold about a million bacteria. Professor Jody Deming believes that as the poles warm, there will be more and more of these meadows, because there will be more and more open sea that turns to thin ice in winter, and her team is eager to discover what the bacteria living in the frost flowers are doing.
Exploring the links from the NPR link with Robert Krulwich (5) leads to citations of professionals articles that explain the formation of Frost Flowers that form on frozen surfaces such as those in the Arctic and Antarctic.
- Alfred Wegener: Haareis auf morschem Holz. Die Naturwissenschaften 6/1, 1918. S. 598–601.
- Gerhart Wagner: Haareis – eine seltene winterliche Naturerscheinung. Was haben Pilze damit zu tun? SZP/BSM 2005.
- Gerhart Wagner, Christian Mätzler: Haareis auf morschem Laubholz als biophysikalisches Phänomen. Forschungsbericht Nr. 2008-05-MW. Universität Bern. 2008. (PDF-Download)
- Gerhart Wagner, Christian Mätzler: Haareis - Ein seltenes biophysikalisches Phänomen im Winter. Naturwissenschaftliche Rundschau 62(3), S. 117 - 123 (2009), ISSN 0028-1050
- Robert Krulwich (December 19, 2012). "Suddenly There's A Meadow In The Ocean With 'Flowers' Everywhere". NPR. Retrieved December 30, 2012. "It was three, maybe four o'clock in the morning when he first saw them. Grad student Jeff Bowman was on the deck of a ship; he and a University of Washington biology team were on their way back from the North Pole."
- Jeff S. Bowman and Jody W. Deming (January 21, 2012). "Elevated bacterial abundance in laboratory-grown and naturally occurring frost flowers under late winter conditions". University of Washington School of Oceanography and Astrobiology Program. Retrieved December 30, 2012. "ABSTRACT Sea ice has been identified as an important microbial habitat, with bacteria and other microbes concentrated in the brine inclusions between ice crystals.... The presence of elevated numbers of bacteria in frost flowers may have implications for the previously observed chemical reactions that take place in them, especially if microbial activity can be shown to occur in this unique low temperature, low water"
- Means, D. Bruce. "Blossoms of ice: these delicate "flowers" sprout only in winter, but you won't find them catalogued in any herbal". Natural History. February, 2004.
Distinguishing the two types of Frost Flowers and the confusion that has ensued== External links ==
|Wikimedia Commons has media related to Frost flowers.|
- Ice Ribbons in East Tennessee
- Extruding Ice from Steel Fences and Pipes with Diurnal Freeze/Thaw
- Frost Flowers Photo Story
- Guide to Frost
-  - Frost flowers (54 pictures) in Bambesch, Luxembourg, Jan.02.2010
- Crystallofolia (‘Frost Flowers’), with Stems of Frostweed (Verbesina virginica) & Marsh Fleabane (Pluchea odorata)
- Frost Flowers from the Mount Catria
- Geheimnisvoll und wunderschön - Wenn Eishaar aus Altholz wächst, Leonardo radio feature in WDR 5 (German)
- Hair ice photos for WDR 5 Leonardo feature (German)