Blossoms of ice: these delicate "flowers" sprout only in winter, but you won't find them catalogued in any herbal

Natural History, Feb, 2004 by D. Bruce Means

Scientific discoveries don't always burst into bloom overnight, accompanied by shouts of "eureka!" Some take years to crystallize in one's slumbering consciousness, before they finally flower. Passing through a rich hardwood bottomland one cold winter's morning in 1976, I noticed white reflections from icy formations on the forest floor, but my quest was for an eastern diamondback rattlesnake that I was radio-tracking, and so I paid them no further mind. A couple of winters later, when I chanced to see them again, their unique shape--like a taffy of ice, pulled into swirling loops and bows--seemed worth a photograph or two. By the time I returned with a camera, though, all had melted.

At the time, I was director of the Tall Timbers Research Station, nestled in the rolling red hills of north Florida, near Tallahassee. Other field biologists who worked and lived on the 2,800-acre site were just as puzzled by these icy wonders. None of us knew whether they were biological, geological, or meteorological phenomena, let alone when to expect them or where to look for them. And any chance to study them would be as fleeting as catching a whisper on the wind. I decided to plan ahead, but the next several winters came and went without any sightings.

Finally, on the night before Christmas, 1983, the stage was set. After an unusually warm autumn, without a single frost, the forecast warned of the overnight arrival of what (for Florida) would be a blustery cold front. Before sunup, I stole out of the house, camera in hand, determined to capture my elusive quarry.

About a mile from the house, in the same bottomland where I had seen them before, I panned my flashlight over the leaf litter. Each leaf sparkled with the fine frost crystals that blanketed the whole world that morning, but sadly ... nothing out of the ordinary.

The ground crunched as I walked. I began to lose heart for the search, recalling fruitless winters past. Then my light played across something white, glistening on the distant ground. There, at last, were my "ice flowers," though they are not flowers at all. (Some call them "frost flowers," though they are not true frost, either.)

I lost no time investigating them before they vanished, shortly after sunup. Ice flowers can be as small as a Ping-Pong ball or as large as a grapefruit. They grow out of the fibrous bases of the perennial known as white crownbeard (Verbesina virginica). During the growing season the plant is undistinguished, looking rather like its relatives ragweed and dogfennel. In winter, its stems are merely dried-out sticks, which mark where its roots will put forth new shoots in the spring. Curiously, early botanists called the plant frostweed. Related plants, such as yellow ironweed, as well as an unrelated frostweed, Helianthemum canadense, also bear ice flowers. Why all plants do not yield such "blooms" is not known.

On close inspection, I saw that the "petals" of my ice flowers push their way through the vascular bundles of the dead stems: Water from the roots is drawn up the stems (either as part of the plant's natural transportation system or through capillary action) and expands as it freezes, breaking the stem walls and creating a flow of ice. The leading edge of the ice freezes to the stem's papery bark, and as the ice grows it is lifted upward by the attached bark, forming delicately curved, lacy ribbons.

Ice flowers are most common during the first frosts of late fall or early winter, depending on latitude; in Florida we have also seen them as late as February. They occur particularly after a wet autumn, when the roots have become saturated with water.

Ice flowers "grown" by the same plants during later freezes in the same winter take on entirely different shapes, often becoming more compact, like true flowers. The bark of the woody stems has already been peeled upward by the first freeze, and so it is no longer available to shape the growth of new ice flowers.

Director of the nonprofit Coastal Plains Institute in Tallahassee, Florida, since 1984, D. BRUCE MEANS ("Blossoms of Ice," page 36) began his career as a research biologist at the Tall Timbers Research Station, near Tallahassee. Means has appeared in a number of television documentaries, including the National Geographic series Snake Wranglers.