The Magic of Frost Flowers

November 12, 2021  |  Permalink

Now that autumn is in full swing, it’s easy to be overcome by feelings of finality. Winter fast approaches, the days shorten and soon much of the plant and animal life will go dormant. The first frost has come and will soon be followed by the first hard freeze, depending on where in the state you reside.

Despite all of these seasonal changes, nature is never static. Even as she sleeps in winter’s silent repose there are always wonders to be seen. Exploring the great outdoors during winter offers unique experiences which cannot be enjoyed during the warmer months.

One very special phenomenon occurs during autumn that often goes unnoticed, but which I look forward to every year.

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Only a few short weeks ago we were enjoying the white blooms of Frostweed (Verbesina virginica), a tall plant in the aster family that blooms in fields and roadsides across most of the state. These plants have just finished supplying vital nectar to late season pollinators and then releasing their seeds to supply the next generation.

hairstreak on frostweed

deer and frostweed

This species is a perennial, remerging from the same root system year after year. In case you have ever wondered where it gets the name Frostweed, you need only to set out early in the morning after a cold, still night in November. If you manage to locate some of these plants you will be treated to one of the most magical forms of freezing water, a phenomenon known as “frost flowers.”

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These plants release moisture from their stems and root systems which ruptures the epidermis (outermost layer) but leaves the rest of the plant intact.  If the ground is not yet frozen, the atmosphere is cold enough and the air still enough, this moisture freezes into delicate ribbons and curls.

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These can take on such whimsical forms it is as if they have whirled and danced straight out of a child’s fairy tale.

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They go by other names as well: rabbit ice, frost ribbons, ice flowers or ‘Eisblatt’ (“ice leaf”), if you are German. Bob Harms from the Plant Resource Center at the University of Texas coined the technical term crystallofolia to describe this phenomenon.

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It is so beautiful and mysterious, but why on earth does this happen? To be truthful, botanists aren’t entirely sure.

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It is theorized that by releasing this excess moisture the plants prevent damage to their cells by forming ice crystals. If this is the case then why do they use this method and not other plants? There are very few plant species the world over that exhibit this phenomenon. In addition, the amount of moisture released exceeds the amount of sap residing in the plant, so it must be augmented by additional moisture pulled from the earth. This sap is in fact supercooled, a state where liquid is below the freezing point without solidification or crystallization. Upon exposure to the atmosphere it will freeze instantly.

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The first frost flowers to emerge are usually the most magnificent, since they are releasing more moisture. As winter progresses the ice formations become smaller and closer to the ground, but they can be viewed as late as January.

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Some sources cite other species of Verbesina, namely Verbesina alternifolia (Wingstem) as producing crystallofollia as well, but I have never witnessed this. Both species often occur together and I have never seen V. alternifolia with frost flowers, nor have other recent observers. I think this mistaken belief arose from misidentification or confusion over common names.

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If you wish to view this wondrous phenomenon keep an eye on the forecast during the fall. If it looks as though nighttime lows are going to fall into the upper 20’s (28 degrees F appears to be the magic temperature), especially on a clear night when the wind is still, set your alarm and strike out early. These ice formations are incredibly delicate and melt fast with the rising sun.

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While I know of many who pack away the hiking boots during the colder months, I would encourage you to not cease your explorations when it gets cold and dreary. There are always new wonders to behold!

About the author

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Holly Taylor got her start with Tennessee State Parks as a Seasonal Interpretive Ranger in 2006, working six years at Edgar Evins State Park before working as a wildlife presenter for the Natural History Education Company of the Mid-South. She took time off to stay at home with her son before returning to TN State Parks as the assistant to State Naturalist Randy Hedgepath in 2018. She graduated from TTU in 2009 with a B.S. in Conservation Biology and also serves as the chapter coordinator for the Cumberland Mountain Chapter of the Tennessee Naturalist Program. She has a life-long passion for the natural world and loves nothing more than sharing that passion with others.