Ice flowers, also known as frost flowers or ice ribbons, are a natural phenomenon observed during the cold season. These ephemeral formations are not frozen dew or atmospheric frost. Instead, they are extruded ice that forms directly from the stems of certain plants, appearing as wispy, paper-thin curls or ribbons. Their formation results from a complex interplay between plant biology, physics, and specific environmental conditions.
Defining Ice Flowers and Ice Ribbons
Ice flowers are sometimes referred to by the scientific term “crystallofolia.” They are thin, wavy ribbons of ice extruded from the stems of a select few herbaceous plants. Although not true flowers, they earned their common name due to their intricate, petal-like appearance.
These structures typically form near the base of the stem, extending outward as a delicate, white excrescence resembling spun glass. They are most frequently observed on species within the genus Verbesina, such as white crownbeard (Verbesina virginica) and yellow wingstem (Verbesina alternifolia), often collectively known as “frostweed.” Wild dittany (Cunila origanoides) is also known to produce these unique ice formations.
The Scientific Mechanism of Formation
The process begins with the roots, which remain active and draw liquid water from the unfrozen soil through capillary action. This action pulls water up into the plant’s vascular system against gravity.
As the water column reaches the stem portion exposed to sub-freezing air, it begins to freeze. Water expands by about nine percent when turning into ice, creating immense internal pressure within the rigid stem. This pressure ruptures the stem’s outer layers, forcing liquid water and sap to exude through vertical fissures or slits.
Once the liquid is pushed through the cracks and contacts the freezing atmosphere, it instantly solidifies into a thin layer of ice. As more water is continuously drawn up and forced out, it pushes the previously formed ice layer away from the stem. This continuous extrusion and freezing process creates the characteristic wavy, ribbon-like structure.
Necessary Environmental Conditions
Ice flowers require a specific set of environmental circumstances to form. The air temperature must drop below freezing, typically hovering between 27°F and 32°F (around -3°C to 0°C). If the air is too cold, the delicate structures can sublimate away rather than melt.
Crucially, the ground must remain relatively warm and moist, preventing the soil and the plant’s roots from freezing solid. This temperature difference between the unfrozen ground and the freezing air allows the roots to continue absorbing and transporting liquid water to the stem. The structures are temporary, often lasting only until the morning sun causes them to melt.
The phenomenon is most common during late fall or early winter, coinciding with the first hard freezes. Since the formation requires an intact stem that retains structural integrity and liquid, the event is often a once-per-year occurrence for an individual plant.