Ice Ribbons, Frost Flowers, Blossoms of Ice or whatever they might be called


Dr. James R. Carter, Professor Emeritus

Geography-Geology Department

Illinois State University, Normal, IL 61790



December 27, 2003, a crisp and sunny day, perfect for a hike.  Greg and I went to Big Ridge State Park along the south side of Norris Lake.  Soon we came upon a cut off log with a giant icicle extending out of the lower end.


It must have been below freezing for many days to get an icicle of this width and length.  But, it must have been warm enough in the log to keep the water flowing so the icicle would keep getting a supply of water. 

The inside of the log would be insulated from extremes of the daily fluctuations in temperature so water could continue to flow even when the air temperature drops below freezing.  And, it must have been quite wet for the log to absorb so much water like a sponge and then continue to release that water over a few days.

In this view of the icicle we see stress lines and ridges showing how layers of ice built up the icicle. 

And this was not the only case of icicles forming at the lower end of cut-off logs, as shown in another example below.


A little later I noticed white puffs off to my right, as though someone had dropped tissues.  I looked closer and saw that these objects were ribbons of ice.  They were not growing out of the ground as ice wedges do.  These ribbons seemed to be hanging from branches.  The more I review this photo I suspect the ice has slid down the twigs from the original position.  The little patch of ice on the lower twig on the left makes me think the larger glob of ice was once located here.

The ribbon above is made up of loops seeming to hang down from the twigs.  The ribbons show parallel bands similar to tree rings.  Based on what others have said about these, I now know the ribbons are extruded from the stems of these plants. 

In the example below you can tell the size of the ribbons by comparing them to the Oak leaves on the ground.  I originally thought this ribbon of ice radiated out from the node at the junction of the stems.  I now realize it was extruded from the stem with more ice being extruded at the bottom than at the top.  Thus, it appears to have rotated around the junction of the stems.  This same process seems to have occurred in the second ribbon at the bottom.  I am not ready to explain what produced the tight spiral in between these two fan-shaped ribbons.

Below is one that seems to be curled up along one edge.  That edge does not appear to have broken off, but perhaps it was broken and differential melting has produced this scalloping.

We broke off a piece and looked through it.  These ribbons of ice are very thin, as shown by the piece in Greg's hand.  In this example the parallel bands look like growth rings, but it likely these striations are formed by variations in the width of the slit from which the ice was extruded.

Below is another example, in this case above a non-leafy surface.  This demonstrates leaves are not a required component of this process, but the stems are present.

As I remember all of these ice ribbons were found along a north-facing slope.  In December 2004 I returned to the Park to see if I could find the place where I saw these ice ribbons the year before.  I did not find that place but I did find some ice ribbons or ice flowers in another place and in somewhat different forms.  There are two pages showing what I found in 2004.

In 2005 I found such ice formations in northern Kentucky and in central Virginia.  Check these out, for they are somewhat different than what I show here but they are the same things.

In fall 2004 I turned to the Web to see if I could find any pages telling about such things.  I searched on 'ice ribbons' and got a hit on a reprint of a four-paragraph article published in 1933 by D. S. Libbey in Nature Notes from Crater Lake National Park.  Libbey wrote:

  "Ice ribbons are prone to occur in the chill of early winter when the ground is neither frozen nor covered with snow. The Cunila - Cunila origanoides - found up and down the Appalachian highland system is the favorite plant on which the ribbons form. Frequently similar ice ribbons have been observed growing from the stems of dead plants and weeds on the frosty slopes of the "hill" of our central plateaus."  Libbey, 1933 reprinted  

A web search on 'ice blossoms' turned up a web summary of an article by D. Bruce Means in Natural History, February 2004.  Means clearly describes what we encountered on our hike and notes that they are quite infrequent.  It took a few years before he had his second sighting of these beauties of nature in a forested area in north Florida.  He refers to these as ice blossoms in his title and as ice flowers in the article and notes that others have called them frost flowers.  He names the species of perennials on which these are known to occur--white crownbeard, yellow ironweed, and Helianthemum canadense.  White crownbeard is sometimes known as frostweed.

  "On close inspection, I saw that the "petals" of my ice flowers push their way through the vascular bundles of the dead stems: Water from the roots is drawn up the stems (either as part of the plant's natural transportation system or through capillary action) and expands as it freezes, breaking the stem walls and creating a flow of ice. The leading edge of the ice freezes to the stem's papery bark, and as the ice grows it is lifted upward by the attached bark, forming delicately curved, lacy ribbons."  Means, 2004  

This online article by Means does not include a photo but the 2-page article in Natural History does contain one large photo.  Means shows nine photos on his web page, and references to his articles about these formations.  Means had a brief article on ice flowers in the November 2004 issue of National Geographic.  The story of Means trying to find these ice flowers was the subject of an article in the Tallahassee Democrat by Sharon Rauch.  That article is online and makes for interesting reading.

Means stated that these ice ribbons do not last through the day but on shaded, north-facing slopes I could believe they might last a few days.  The size of the icicles hanging off the ends of the logs tells me that the previous night was not the first night with freezing temperatures. On the other hand, I am more certain that the ice in the first photo has slid down the stem and the ice was melting when I took the photo.

Betty Swihart in Missouri Conservation Online, writes about Frost Flowers.  She distinguishes 'frost flowers' from 'ice flowers' which she says are created by water condensing and freezing quite quickly.  Based on my experience, I think that in the ice flower situation she describes water vapor condenses as frost on such things as manhole covers, not as water which then freezes.  But still, she uses the term ice flower for something different from what we are talking about here.

Swihart gives very clear descriptions of how frost flowers form on stems and notes the same two species mentioned by Means.  Anyone interested in this subject should read her description of how these form.  She notes that they can form on the same flower in successive freezes.  Shihart's original article was published in Missouri Conservationist, October 2000. 

The naturealmanac site has a page showing four examples of ice flowers sent in by others.  They lost the name of the person capturing the first image, but Steve Haskins owns the other three photos.  The flowers in those photos are most similar to the flowers I found.  Steve is from Ohio and supposedly found his examples in Ohio.  Naturealmanac also has an article about the plant Wild Oregano, noting:

  Wild Oregano (Cunila origanoides) . . . Found on dry, rocky woodland slopes this foot-high member of the mint family has sprays of tiny lavender flowers and is one of the last woodland plants to bloom. . . has another claim to uniqueness since it's the only plant in our flora to consistently produce "frost flowers".  Frost flowers result when freezing temperatures cause the sap to freeze and then while expanding extrude through ruptures in the stem creating long ribbons of ice.  

Mims has an online article on Frost Flowers as seen in south Texas.  His presentation shows a good photo of one of these near the ground.  He notes they are also called frost castles or ice castles and he notes that these occur in several species of plants, as:

  Several species of plants produce frost flowers. The plants that produce them on our place are white crownbeards (Verbesina virginica). These plants have large leaves and can be taller than 6 feet. They are capped by a rounded cluster of small, white flowers. They are also known as tickweed, frostweed and ice-plant.  

Mims goes on to discuss how these must form and gets into various terminology relating to frost.  I agree with Mims that these are not frost, which comes about as water vapor is deposited on to a surface in crystals of ice.  I have gone through many ideas of how these creations are formed.  I thought there must be a ice in a somewhat plastic state that is extruded through the thin cracks in the plant stem.  I tried to simulate this by freezing water in many containers with slits and scars.  It was stimulating to try many different ideas but it did nothing to explain how these ribbons of ice form.

Then there was an article in Weatherwise (Jan/Feb 2005) about the formation of ice spikes in ice cube trays.  To explain this phenomenon they turned to Dr. Charles Knight at the University Center for Atmosphere Research.  So, I contact Dr. Knight for his perspective on the formation of these objects.  At about the same time I received an email from Dr. Ken Orvis at the University of Tennessee, Knoxville, offering an explanation.  They note that as ice forms crystals inside the stem of the plant water moves towards the ice crystals and passes through the stem. As the water emerges into the air that is below freezing the water freezes into ice crystals on the outside of the plant.  As more water emerges it freezes and pushes the existing crystal further out.

I need to spend more time in the literature but I understand the basic process.  The presence of the striations in these ribbons of ice tell us that different size of droplets and ice crystals grown under different conditions. 

I keep finding sites on the to photos of these ice ribbons.  The site of the southern Missouri Ozarks has four very attractive photos and a discussion of how the ice forms.  Sorry to say this discussion does not provide answers to all of the questions I pose above. 

In a lengthy Cloudland Journal for November 2003, Tim Ernst shares observations about his Arkansas environment.  In his entry for 11/24/03 he talks about going out on a cold morning to find these frost flowers in his garden where he often finds them on ". . . the first really good cold snap of the season."  He notes "I can always count on this spot for the best frost flowers" but they were not here this day.  On 11/25 the flowers appeared and the author has six photos of those frost flowers.  There are some beautiful images here.  The author notes that within about 100 yards there were more than 150 frost flowers.  Interestingly, he observed that it was not as cold this day as it was the day before.  The author contributes to the discussion of how these form when he wrote:

  Here is some info about frost flowers (stolen from Don Kurz's OZARK WILDFLOWERS guidebook on page 74 - the best wildflower book available ANYWHERE!). The plant that the flowers form on is called "White crownbeard," or "Frostweed." From Don's book: "These are ribbons of ice oozing out of cracks at the base of the stem. Sap from still-active roots freezes as it emerges from the dead stem, growing like a white ribbon as more fluid is pumped out."  

Oh, I found a good web site for what someone calls ice flowers but these are photos of the work of Jack Frost on windows.  The images are beautiful but they are very different from the ice ribbons or frosts flowers shown above.  NASA has a web page discussing and defining Frost Flowers, which are true formations of frost.  They have an attractive image of what they call frost flowers.

How nice it is that there are beautiful flowers to be seen when the temperature drops below freezing, whether in the woods or on the window.  We do not have to wait until spring to see flowers--look around.

And what are these things called?  There is no standardization of terms.  While one person calls these ice flowers, another person uses that same term to apply to something different.  I prefer ice ribbons, based on their form.  But, I appear to be in the minority.

Please send any thoughts and comments to me--Dr. Jim Carter at


one of the pages of Dr. James R. Carter