The Elegance of Frost Flowers

Forrest M. Mims III

This winter has been frost flower season in South Central Texas. The unseasonably warm winters of the past several years have kept early risers from enjoying one of nature's most exotic visual treats.

A frost flower is one of several names for the satin-like whorls and ribbons of ice that decorate the lower stems of white crownbeard (Verbesina virginica) plants on freezing mornings. These strikingly beautiful formations are also known as ice or frost castles.

White crownbeard is an inauspicious name for a large and attractive native plant that prefers shady areas and can grow to a height of more than two meters (six feet). The plants have large leaves, and during fall they are capped by a spray of little white flowers that can be larger than a dinner plate. The flowers attract flocks of butterflies, bees, wasps and various other insects.

White crownbeards save their most beautiful displays for winter. If you live where white crownbeards and other frost plants are found, you may have seen their frost flowers without knowing it, for from a distance they resemble discarded wads of tissue scattered along roadsides on freezing mornings.

A closer look will reveal that these white splotches are intricately sculpted formations of translucent ice. After sunrise, the glistening flakes and ribbons of ice fall to the ground and quickly melt away.

Figure 1. Natural ice sculptures called frost flowers form at the base of white crownbeard plants. Photograph by Forrest M. Mims III.

This winter's first frost flowers along the Geronimo Creek appeared on December 17. I put on multiple layers of clothing and spent several hours lying on the cold ground photographing many of them. More frost flowers appeared during subsequent freezes, but each time the displays became increasingly smaller. This is because the ice splits the stems of the white crownbeards and exhausts their supply of moisture.

Several years ago I used a small elapsed time camera (the discontinued Pentax Optio 33WR) to record the collapse and melting of frost flowers after sunrise (see here). This year my goal was to record the formation of a frost flower, an event I have never observed.

During a cold snap the night of January 2, 2008, I put on layers of clothing and prepared the camera equipment but did not set it up outdoors until checking to see if frost flowers were forming.

Around 10:30 PM, a thin ribbon of ice began emerging from the base of a white crownbeard stem when the temperature had fallen to about -3 C (27 F). This was my first view of this amazing phenomenon. Ten minutes later the ice ribbon had grown noticeably larger, so I set up two elapsed time cameras in the woods (a Pentax Optio 43WR and a Canon 40D with external interval timer).

Several 99-photo sequences were made of frost flowers being formed. The photos were made at intervals of one or two minutes. The best sequences were made beginning around 1:30 AM.

When these sequences were strung together, they became astonishing movies that show silky ribbons of translucent ice emerging from plants and curving into beautiful frost flowers.

I've compiled some of these sequences into a short movie that you can see here. Or go to www.youtube.com, enter “fmims” in the search box, scroll down the list of my nature videos and click on “Frost Flowers.”

Be sure to see Glenda Wolin's frost flower photo in the "Gallery" department of this installment of The Citizen Scientist.