Frost Flowers, Hair Ice and Needle Ice

Tis the season for observations for these phenomenon to be prevalent. I have been looking at some observations that were tagged as Hair Ice in the Southeastern US and they looked more like the phenomenon I have known as Frost Flowers. I did some searching around and found this excellent resource that complies tons of research and information on these phenomena:

A few thoughts I thought I would put out for discussion.

  1. Hair ice is a fungus that grows from bare wood on the ground and causes very fine separate ice crystals to grow. It seems to be concentrated in Europe and the Pacific NW. Here is a good example:
  2. Frost flowers are wide ice crystals that grow from standing plant stems, but there does not seem ot be a fungus involved. They are usually found on Frostweed (Verbesina virginica). Some good examples are here:
    However the website above references some other species of plants that this phenomenon is reported in.
    Every once in a while users will add Needle ice as an observation thinking it is a fungus or something, but it is simply ice crystals growing vertically out of the soil (I’m not going to search for a good example right now. :) )

The point of my post and possible discussion fodder is that we need to look closely at observations to distinguish between Hair Ice and Frost Flowers AND we might need to be careful assuming that all Frost Flowers are coming out of Frostweed.

I spent some time yesterday and looked though quite a few observations from the Southeastern US IDed as Hair Ice that I believe are Frost Flowers instead. I put my ID as Vascular Plants because in many cases there were not many identifying features of the plant in question just a bare stem. I’m sure I irritated some in the Hair Ice camp, but I have yet to see anything from down here that looks like that fine fluffy ice produced associated with the fungus.

Finally for future reference it might be helpful to add a tag to observations of plants with these ice growths as “Frost Flowers” since it is a physical not a biological feature and is otherwise hard to search for unless someon has identified it as Frostweed. Otherwise observations of this phenomenon that might possibly turn up are “lost” or at least very hard to find. Here are the other know plants according to this researcher (Source

  • Dittany or Stone Mint, Cunila origanoides – widely recognized

  • White Crownbeard or Frostweed, Verbesina virginica – widely recognized

  • Yellow Ironweed or Wingstem, Verbesina alternifolia – widely recognized

  • Frostwort, Frostweed, or Rockrose, Helianthemum bicknellii and Helianthemum canadense – widely recognized

  • New York Ironweed, Vernonia noveboracensis – from Jan Donaldson of middleTennessee.

  • Buttonweed, Diodea virginiana – from Dr. Bruce Means of north Florida

  • Marsh Fleabane or sweetscent, Pluchea odorata from Dr. Bob Harms of Texas

  • Firebush, Hamelia patens – from Dr. Bob Harms of Texas

  • Fleabane, Pluchea camphorate – from some old references

  • Plumbago, Plumbago auriculata – from Chuck Hubbuch of north Florida

  • Lantana New Gold, Lantana x hybrida’New Gold’ – from Chuck Hubbuch of north Florida

  • Trailing Lantana, Weeping Lantana, Lantana montevidensis from Chuck Hubbuch of north Florida

  • Lantana, Lantana camara – from Jan MacDougal of South Carolina

  • Pentas, Star Flower, Star Cluster, Pentas lanceolata – from Jan MacDougal of the low country of South Carolina

  • Scarlet Sage, Texas Sage or Salvia, Salvia coccinea – from Jan MacDougal of South Carolina

  • Scrambling Sky Flower, Thunbergia battiscombei – from Jan MacDougal of South Carolina

  • Black Eyed Susan, Thunbergia alata – from Jan MacDougal of South Carolina

  • Red Flowerd Manettia, Manettia coccinea – from Jan MacDougal of South Carolina

  • Madagascar Periwinkle, Rose Periwinkle or Vinca Coral – Catharanthus roseus – from Jan MacDougal and my own observation

  • Victoria Blue Salvia, Salvia Farinacea – from my own yard in Illinois

  • Chinese Plumbago or Willmott Blue Leadwort, Ceratostigma willmottianum from Sally Twyman of southwestern England

  • Corsican Hellebore or Corsican Rose, Helleborus argutifolius – from Sally Twyman of southwestern England

  • Germanders, Teucrium arduini – from Richard Wanner in Switzerland

  • Colombine, Aquilegia – from Richard Wanner in Switzerland

  • Purple Coneflower, Echinacea – from Richard Wanner in Switzerland

  • Hemp-agrimony, Eupatorium cannabinum – from Richard Wanner in Switzerland

  • Meadowsweet, Filipendula ulmaria – from Richard Wanner in Switzerland

  • St. John’s Wort, Hypericum perforatum – from Richard Wanner in Switzerland

  • White Deadnettle, Laminum album – from Richard Wanner in Switzerland

  • Throw-wort, Lion’s Ear, and Lion’s Tail, Leonurus cardiaca – from Richard Wanner in Switzerland

  • Oregano, Oreganum vulgare – from Richard Wanner in Switzerland

  • Bladder cherry, Chinese lantern, Japanese lantern, or Winter cherry, Physalia alkakengi – from Richard Wanner in Switzerland

  • Alpine Pasque Flower, Pulsatilla halleri – from Richard Wanner in Switzerland

  • Figwort, Scrophularia nodosa – from Richard Wanner in Switzerland

  • Creeping Thistle, Cirsium arvense – from Richard Wanner in Switzerland

  • Spear Thistle, Bull thistle, Plumed thistle, Roadside thistle, Cirsium vulgare – from Richard Wanner in Switzerland

  • Stinging Nettle or common nettle, Urtica dioica – from Richard Wanner in Switzerland

  • Loosestrife, Lysimachia punctata – from Richard Wanner in Switzerland

@sambiology I would love to know your thoughts on this.


Here is an example found on Scutellaria incana:

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I have seen it on Salvia coccinea. I haven’t posted my photos on iNat since the Salvinia was cultivated.

Has anyone confirmed that the hair ice in the Pacific northwest (or anywhere in North America) is produced by E. effusa? The research published in 2015 was about samples from Germany. I glanced through the iNat observations from the PNW, and they are all photos of the ice, rather than the fruiting fungus. Mushroom Observer has photos of the fruiting fungus without ice, but only from Austria. It is possible that other species of fungi produce hair ice in different regions.


I am not sure. I am curious as to ideas of how to document this. In some ways the ice might be indicative of the presence of the fungus (kind of like how a burrow is evidence for a Gopher tortoise ex: but does not directly show the organism in question. Would the threshold for evidence for an observation have to be a microscope slide with fungal hyphae (or spores or or whatever it is in the case of this fungus) or is the characteristic ice “growth” “good enough”? Same with the Frost Flowers. Many of the observations assume it is Frostweed that it is appearing on but that may just be an artifact of the AI designation. Should the ID be the plant and then in the notes or observation field specify “Frost Flowers”? I had no idea what a rabbit hole I was wandering down into when I first started poking around with this. :)

Here is an example of a Needle Ice observation:
Since observations like this do not include an organism they should just be IDed as “Unknown” and the “No Evidence of an Organism” be noted under Data Quality.


If there is literature to back up the association of the ice formation to the species, then I can’t see why it should not be used as “recent evidence”. Perhaps with a link/reference to the literature as a comment or in the description so that anyone not aware of it can drill down and learn…

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Thanks for starting this thread. I found frost flowers for the first time a couple of months ago with a vague notion of what the cause of the phenomenon was. I forgot to upload after hesitating because I wasn’t sure if it was caused by a fungus or not. After reading this thread, I went back and was happy to see I got pictures of the leaves and flower heads of the plant, as I otherwise would have assumed it was frostweed (it was common dittany).

Would a project be a good way of compiling observations including frost flowers?


I had thought of starting a project to try to compile these observations into one convenient spot. Haven’t pulled the trigger yet. I actually corresponded with Dr. Carter (the author of the link I shared He is not on iNaturalist, but was keen to find observations from other parts of the country and especially on different species of plants besides Frostweed. He actually specifically asked if there were any for Common Dittany and he seemed impressed by the platform when I was able to quickly search and find him some observations.


Because I am not very knowledgeable about frost flowers or the plants on which they form, I do not feel qualified to be a project creator/curator. However, if such a project existed, I would be happy to add observations to it or help in any other way

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