In a process called Ice Segregation cold water moves through a medium toward the presence of ice, freezes at the interface and adds to the ice. Ice Flowers and Frost Flowers are the most common names for the growth of ice on plants stems through the process of ice segregation. .
Figure 1 - On the left are Ice Flowers on two stems of Dittany Cunila origanoides. On this plant the water seems to emerge from the stems in only a couple of places giving two curtains of ice on each stem. This plant was in east Tennessee and had not be cut or trimmed. On the right is an Ice Flower on cut-off stems of White Crownbeard / Frostweed Verbesina virginica. These stems were in northern Kentucky along a road. The plants had been cut by mowing along the highway. In this case ice emerged from many places around the stem to produce more full flowers. Note the white frost on the green leaves in the photo on the right. While it is common to have frost occur near and on Ice Flowers, they are not produced by frost.
Ice segregation occurs in many places at the surface of the Earth where we have freezing and thawing. When this occurs on some pieces of dead wood we see Hair Ice . When this occurs at or near the surface of soil it produces Needle Ice, which takes the form of strands of ice rising vertical from the surface or near surface of the soil. And, it has been found that ice segregation works through small rocks to produce what is called Pebble Ice . Ice Segregation is also known to occur in subsurface environments and can be a significant geologic force in areas with permafrost and in periglacial environments.
On the Names of these Ice Formations and the Plants
Dr. Bruce Means was the first person in current times to publish broadly on these ice formations on plants and calls them Ice Flowers . Some of the plants which support such growths of ice are called frostweed and some call the ice formations Frost Flowers. Many people who find such growths of ice often give them names that are descriptive of what they see. In addition to Ice Flowers and Frost Flowers you may see names such as Ice Ribbons, Ice Fringes, Ice Filliments, Rabbit Ice, Ice Castles, Frost Castles, Ice Leaf and Eisblatt. Dr. Robert Harms has proposed the name Crystalfollia based on Latin roots - basically translated as Ice Flower.
Although often called Frost Flowers it should be noted the formation of this ice is NOT a deposit of frost. But many photos of Ice Flowers show that frost has occurred nearby and in some cases frost is deposited on the Ice Flower. It should be noted Dr. Forrest Mimms III used the name Frost Flower in his online video showing the growth and display of such ice.
There are only a few plants that have been identified with the formation of this type of ice. White Crownbeard or Frostweed, Verbesina virginica, and Common Dittany, Cunila origanoides, are the two most common producers of Ice Flowers in North America. A few other plants produce such ice forms under the proper conditions. Carter has compiled a list of flowers reported to have produced Ice Flowers. However, this list is not definitive and now that more persons are learning about the products of ice segregation we should expect that persons will find other plants that produce similar ice and inform us of these findings.
Descriptions from the Past
In 1988 Lawler published a bibliography of Needle Ice listing 267 references dating back to 1824. Within these many references are citations that definitely refer to what are Ice Flowers.
One of these citations was the letter of J. F. W. Herschel dated January 12, 1833, in Philosophical Magazine, 3rd series, 110-111, entitled: "Notice of a remarkable Deposition of Ice around the decaying Stems of Vegetables during Frost." He wrote that years before he had found ice ". . . to incrust the stalks in a singular manner in voluminous friable masses, which looked as if they had been squeezed, while soft, through cracks in the stems." Then on January 11 he found a similar formation of ice which he described as ". . . seemed to emanate in a kind of riband- or frill-shaped wavy excrescence, -- as if protruded in a soft state from the interior of the stem, from longitudinal fissures in its sides, . . . the structure of the ribands was fibrous, like that of the fibrous variety of gypsum, presenting a glossy silky surface"
In theThe London, Edinburgh and Dublin Philosophical Magazine and Journal of Science, Third Series of May 1850, 329-342, John LeConte, M.D., of the University of Georgia wrote about many instances of observing frost flowers and needle ice in Georgia. He quotes liberally from Hershel (1833), for he appreciated the words as I do. LeConte also produced some lovely descriptions such as ". . . the traveler who passes along the level roads of this region soon after sunrise cannot fail to be struck with the remarkable accumulations of voluminous friable masses of semi-pellucid ice around the footstalks of the Pluchea which grow along the road-side ditches. At a distance they present an appearance resembling locks of cotton-wool, varying from four to five inches in diameter, placed around the roots of plants; and when numerous the effect is striking and beautiful." p. 330. He observes that in some cases ice had formed on the same plant on consecutive nights "when the wood was not rifted." p. 332. He also makes observations about what we now call needle ice and argues "that both of the phaenomena must be referred to the same cause. If we admit an identity of cause in the two cases, it is obvious that it must be purely physical . . ." p. 336.
So there is nothing new about Ice Flowers but we now have digital cameras to capture such blooms and the Internet to share our findings.
Ice Flowers of Various Sizes in Various Places
Figure 2 - In Virginia I found a stem of Dittany that had a small ice flower. Nearby were many examples of Needle Ice as seen behind the flower and in the image on the left. Thus, if the conditions are right ice segregation may produce ice flowers and needle ice in the same area. And, nearby was a rod of ice which I now know was Pebble Ice.
Once I became aware of Ice Flowers I imported seeds of Verbesina to grow ice where I live. It is much easier to find and monitor the behavior of the plants if they are nearby. After two or three years I found I had two varieties of Verbesina - virginica and alternifolia. The big diffences are virginica has white blossoms and grows ice and alternifolia has yellow blossoms and does not grow ice. Kurz states Verbesina virginica is known as White Crownbeard and Frostweed while Verbesina alternfolia is known as Yellow Ironweed.
Early in one season I found two small growths of ice on stems of green Verbesina virginica . The only other evidence of freezing conditions on that calm morning was frost on a windshield of a nearby car. The ground was still too warm to have frost on the grass so within a small elevation range the temperatures were cold enough to induce the process of ice segregation.
Figure 3 - The two Ice Flowers above are about 3 cm (1.2 in.) long. They are about 10 cm (4 in.) above the ground surface. The plant is Verbesina virginica, with a hairy stem and wings along the stem. While it is tempting to consider plant form as a factor in producing Ice Flowers, the other version of Verbesina has hairy stems with wings and does not produce Ice Flowers.
Later in the season the growth of ice becomes more common and produces larger blossoms, as in the example below. Note that here the stems are still green.
Figure 4 - This Ice Flower is on a stem of Verbesina virginica and forms what I call a scoop. The scoop from base to top is at least 5 cm in length. On the right the focus is on the way the curtains of ice seem to emerge from the stem, forming almost 3 parallel layers or streams. After extending out a little way the curtains of ice merge into one forming one side of the scoop.
Note that on the right side of the stem in this zoomed-in view a curtain of ice has separated slightly from the stem. This is consistent with Ice Flowers for the ice does not penetrate the stem but forms on that surface. It is common to pick an Ice Flower off a stem, or knock an Ice Flower off a stem, for the ice is very tenuously attached to the plant stem. While growing there is a thin film of water between the stem and the ice.
If and when the ice segregation process stops and no new ice is being produced, then the existing ice may become bonded to the stem in a different way if the temperature is below freezing.
Figure 5 - This Ice Flower on Verbesina virginica, White Crownbeard, is viewed from above and from the side. From above we see how the ice seems to emerge from all sides of the stem. I say "seems to emerge" because the ice does not emerge from the stem but water emerges from the stem and becomes ice at the surface pushing the previous ice further out - or growing ice.
As the thin curtains of ice move out from the stem they often bond with other curtains and together move in unusual ways. In this case the curtains merged into two flows and wrapped around the stem as they became ever larger. In the photo on the right we see the bare stem separating the two sweeps of ice. This stem is about 10 cm in height (4 in.)
The example below shows a very complex Ice Flower from probably more than one stem of Verbesina virginica, White Crownbeard. In this case the stems are not visible.
Figure 6 -- This Ice Flower on Verbesina virginica is less coherent than in the other examples above. Here there are thin strands of ice in many places rather than broad curtains of ice. In the middle are overlapping ribbons of ice similar to ribbon candy (close-up on the right). In this case a curtain of ice must have grown out from a stem and encountered a blockage but the ice kept coming and in the process the ice ribbon folded back and forth to create this overlapping pattern.
On the left image there are many deposits of frost on the tan stem and on many of the strands of ice. Frost is the deposition of ice on a solid surface as moisture condenses out of the air when the temperature is below freezing.
It can be quite informative to see how ice grows on the same stems over the season. With the plants in my yard I have seen ice on the same stems at least 20 times during the cold season. Generally ice forms over night and during the heat of the day melts. Then if temperatures fall below freezing the next night new ice is likely to form. Sometimes an Ice Flower will last from one day to the next but when this occurs the quality of the Ice Flowers is likely to be degraded. Sometimes the entire Ice Flower falls off, consistent with the observation that during ice segregation the ice is not attached to the stem.
Figure 7 - These three ice formations are on the same stem of Verbesina virginica. On the left is the first growth that caught my attention, on November 13. That ice melted and the next day the Ice Flower was more full, looking like a bottle brush as the ice extended straight out from the full length of the stem. Note that in this case the strands of ice did not touch each other to merge and form broad sweeps as shown in Figure 5. Perhaps they were not long enough or perhaps there was no wind to blow them together or perhaps something else.
On the right we see the ice that formed 10 days later on this stem was more voluminous and much thicker at the bottom than at the top. In this example many curtains of ice merged together.
I am not able to say if these differences in the appearance of the ice is due to the lenght of time the temperatures were below freezing each day or if the nature of the stems evolves as ice forms on the stem time after time. I do know that at the start of the season ice forms quite high up on the stem and may extend all the way to the ground. I have seen ice extend 75 cm (30 in.) up a stem. But, as the season progresses the ice does not extend as far up the stem.
The most voluminous formations of ice generally occur two to four weeks after the first formations of ice flowers and occur at or near the ground. The later dates are probably because the temperatures are below freezing for a longer time, but perhaps the stems have been transformed by previous growths of ice.
Figure 8 - As the plants die off at the end of the growing season the only water to support the growth of ice has to be pulled up from the soil. By early spring there may be Ice Flowers on the old stems but the Flowers will be no more than 2 cm in height. This shows that the stems are only conduits to wick the water up from the soil to add to any ice produced through ice segregation.
The example on the left shows an Ice Flower on April 2, one of the last days of frost in central Illinois. The first ice of the season was on November 4 - five months before. Note that ice occurs on two stems but a third stem has no ice. Why? Good question.
Ice Flowers on other Plants
The first Ice Flowers I saw were on Dittany Cunila origanoides in Tennessee. Subsequently I saw most of my ice on Verbesina virginica, and that is what I was able to get and grow in my yard. Most of the emails I receive from others show Ice Flowers on Verbesina but on occasion it is ice on Dittany.
Dr. LeConte in 1850 noted the ice he saw was on Pluchea. Pluchea odorata Marsh Fleabane is one of two plants where Dr. Robert Harms finds Crystalfollia - in Texas.
I have received emails from many person who have seen Ice Flowers on other plants, many ornamentals in their yards. And, some Europeans have sent me information on what they have observed. I have compiled a listing of all plants on which persons have reported seeing Ice Flowers.
The first season I had stems of Verbesina in my yard we found ice growing on an ornamental flower. This was on a stem of Red Salvia, a cultivar. The ice was not very attractive but it was an Ice Flower on a plant stem. Surely, it was not the first time ice had grow on a plant stem in my yard but it was the first time I had looked at my yard in that way. Now I look at plant stems everywhere on mornings when it has been above freezing and the temperature has dropped below freezing.
I started planting a variety of ornamentals in my yard to see what happens.
Figure 8 - One of my favorite flowers is Victoria Blue Salvia - Salvia farinacea 'Victoria Blue". It is a cultivar. Last year I found the Ice Flower on the left on November 14 while the blossoms of the flower were still present. The Ice Flowers are relatively small but they display patterns quite similar to that of Verbesina . In this example the Ice Flower is about 8 cm high (3 in.).
The photo in the middle shows an Ice Flower on a cut-off stem of Victoria Blue Salvia. This small flower is about 5 cm (2 in) across. This flower occurred in late December after the ground had been covered with snow for many days and the soil had been frozen. With a warm spell the ground thawed and one day this Ice Flower appeared. Victoria Blue Salvia, like White Crownbeard and Dittany may grow Ice Flowers many times during a winter season.
The Ice Flower on the right is on a stem of Vinca. This stem is not very woody and the ice appears to have split the stem. After this one occurrence there was no stem to support further growth of ice. How much of this ice is from ice segregation and how much is from freezing water in the stem? I suspect some of both because we do not see such ice on other soft plants stems.
Note how this stem seems to have been shattered by the ice. It is not uncommon to have a stem shattered by the growth of ice inside the stem, but this will only happen if the energy flows in ice segregation on the stems gets out of balance and ice penetrates into the stem. But, when the same stems produce ice more than 20 times a year it must not be that common on those plants that are known for growing Ice Flowers.
I was finally able to grow stems of Dittany Cunila origanoides in my yard. These were relatively small stems but they grew Ice Flowers in form similar to that shown on Dittany in Figure 1 -- being only one or two curtains of ice from the stem. Indeed the forms of Ice Flowers on Dittany seem to be significantly different from those on stems of Verbesina virginica, White Crownbeard.
On this page I have shown the Ice Flowers I have found in my limited world. Based on Internet contacts and written works I know these products of ice segregation occur in many places. Dr. Bruce Means finds his Ice Flowers in northern Florida. Drs. Forrest Mimms III and Bob Harms find theirs in Texas. A century ago persons wrote about finding these in Connecticutt and Maryland. Someone found such ice in Wisconsin. Many people in Arkansas, Missouri and Tennessee report on finding Ice Flowers on Verbesina and Dittany. I have had one report of Ice Flowers in New Mexico and on an ornamental plant in Arizona. In 1933 Libby wrote about Ice Flowers on Dittany in Crater Lake National Park in southern Oregon. But, I have not heard of Ice Flowers in the humid Pacific Northwest although there are many reports of Hair Ice , a related product of ice segregation.
I have seen two photographs from persons who found Ice Flowers in the Himalaya of northern India. And, persons in Switzerland who knew about my interest found Ice Flowers on a variety of plant stems and shared photos of them with me. I suspect they occur in many more places than I have heard about because the climatic conditions with necessary freeze and thaw cycles are common in many parts of the world.
There is much more to be learned about Ice Flowers that are produced on stems of some species of plants. Please join the search for examples and share them with us.
http://my.ilstu.edu/~jrcarter/ice/flowers/
