Friday Flower: Crystallofolia (“Frost Flowers”)

Crystallofolia (frost flowers) on dittany (Cunila origanoides).

While hiking the middle stretch of the Ozark Trail’s Wappapello Section, my friend Rich and I witnessed a bounty of crystallofolia, or “frost flowers”.  These fragile, yet exquisite formations are, of course, not flowers at all, nor are they true frost (which forms directly from water vapor without first condensing), but rather are thin layers of ice that form as water is drawn from cracks in plant stems and freezes upon contact with cold air.  As the water continues to be drawn from the plant by capillary action, newly forming ice pushes older ice further out, creating delicate, folded, curling ribbons of ice that resemble many-layered flower petals.  Air trapped within the ice upon freezing imparts a frothy white appearance.

Frost flowers are not an uncommon phenomenon, and I have seen them on more than a few occasions during my frequent off-season hikes.  However, never before had either Rich or I seen the numbers that we saw during our hike on this, the second day of the New Year.  Frost flowers are normally encountered during the first hard freezes of fall when the ground is not yet frozen.  Water in the stems of certain plants expands as a result of the freezing air temperatures, causing vertical cracks to form along the length of the stem through which the ice ribbons are extruded. The formations are rather ephemeral, usually melting or sublimating away by late morning in fall’s typically mild daytime temperatures.  As fall progresses to winter, water stores in the plant stems become depleted after several freezes or locked up when the ground itself freezes, and as a result frost flowers are rarely seen later than December in Missouri. However, it has been a wet and mild fall and early winter, and after an extended period of moisture during December, Missouri was finally gripped by a severe cold spell with lows in the single digits and daytime highs remaining down in the teens and 20s.  The saturated, yet unfrozen ground provided a good source of moisture for plant stems to draw upon, and continuous subfreezing air temperatures allowed frost flowers to persist throughout the days and attain remarkable size. The photo above was taken in late afternoon as a sinking sun shone brightly on the west-facing slope where this formation was seen, persisting in all its fragile glory.

In Missouri, frost flowers are primarily associated with dittany (Cunila origanoides), species of Verbesina (V. virginica, white crownbeard; and V. alternifolia, yellow ironweed), and camphor weed (Pluchea camphorata).  Frost flowers are rarely seen on any other plant in Missouri, and I don’t know what it is about these plants and not others that make them suitable for frost flower formation.  Dittany is a daintly little member of the Lamiaceae, and as such has square stems – perhaps the angles on the stem are prone to splitting.  However, there are many other lamiaceous plants and non-lamiaceous square-stemmed plant species in Missouri that do not form frost flowers.  Likewise, Verbesina and Pluchea belong to the Asteraceae and do not have square stems.  They are, however, larger, more robust plants with thick, pithy stems that may be capable of holding a large amount of water and mature late in the season after most other plants have already dried up, perhaps allowing them to retain sufficient moisture in the stem late enough in the season to allow frost flower formation when conditions are right.  The majority of the frost flowers we saw were on dittany – dainty, delicate, fragile formations 2-3 inches across. However, at the end of the hike, as we were exploring the area around the parking lot, we found a stand of Verbesina (I suspect V. alternifolia), with which some of the most enormous and robust frost flowers that I have ever seen were associated.  Following are additional views of some of the more impressive formations we saw and the plants they were associated with.

Frost flowers on dittany - shaded, protected areas produced the largest formations.

Partial thawing during ribbon formation causes exquisite twists and turns.

Like snowflakes, each frost flower is one-of-a-kind.

Dittany (Cunila origanoides) dried stem, leaves, and fruits.

Verbesina sp. frost flowers were enormous - this one was approx. 5 inches wide.

Dried fruits of Verbesina sp. (poss. alternifolia).

Copyright © Ted C. MacRae 2009

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33 thoughts on “Friday Flower: Crystallofolia (“Frost Flowers”)

  1. How beautiful these formations are Ted. In some ways I can see and appreciate the beauty of winter but I am only to please I do not have to actually live with it.

    • Winter has its ups and downs – I enjoy it for its ups (which include hiking and the chance to see phenomena like this) and find ways to turn the downs into positives (such as having a chance to catch up on specimen work).

  2. I’ve never seen these myself, but I have friends who see them quite regularly in the fall/early winter. I keep hoping that one day I will surprise one on my walks.

  3. Ah! Thank you, Ted! You’ve answered a mystery I stumbled across early last winter and again this. At my parents’ new place there are sections of the trail through their woods that pass through wet grassy areas, and in November, before the snow falls but after things start to freeze, we’d come across these weird ice formations that looked for all the world like clumps of grass but contained no grass inside of them (eg here and here; hard to get a good pic). I hadn’t put much effort into identifying them or the process that made them – but now I don’t have to!

    Those frost flowers are beautiful. It’s amazing what nature does.

    • That is a related phenomenon called “needle ice” or “frost columns”. The same principle applies – i.e., moisture drawn from an unfrozen source by capillary action and freezing upon contact with cold air. However, in this case the water is being drawn from the soil itself rather than plants. I see this mostly on bare patches of loose soil in otherwise vegetated or leaf litter covered areas – the columns tend to lift soil with them as they grow.

  4. It’s always such an exquisite and delicate formation. You’ve really captured it beautifully! We don’t see this often down here, but I always look for it because a good cold snap can lead to some temporary wonders (that promptly melt the same day!).

    • Thanks, Jason. I’ve seen these pretty much every year for the past few years at the start of the winter hiking season, yet I am always enchanted by them when I see them. This year’s rich bounty – lasting through the day – was unlike anything I’d ever seen before.

  5. Beautiful photos. They’re amazing, aren’t they? And you can’t just take a picture of one because they’re all so different! Thanks for sharing.

    • Yeah, we kinda went crazy taking pictures. But I’m glad we did, as it was only after I was going through all of them that I realized how incredibly unique each one was. I may never get another chance to see them in such persistent abundance.

  6. Great photo’s Ted. Maybe one day I will venture out of the tropics and be lucky enough to see one of these. Then again… I get shivers even thinking about the cold!

  7. I’ll have to make it a third Canadian unfamiliar with your beautiful frost flowers. The three genera you list aren’t listed in the Flora of Alberta, so perhaps it is something special about these plants. Or perhaps it just freezes up to fast and too hard here.

    In a way, your frost flowers remind me of Welwitschia mirabilis – although the sprawling, strap-like and ever-growing leaves of Welwitschia are more bizarre than beautiful. Great photos.

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