Skip to content

Ice flowers

2010 January 14

Ice flowers form at the base of only a few plants. Photo by Patrick Coin.

By Ken Moore

Last week, Botanical Garden staffer J.C. Poythress enthusiastically asked whether I had seen the ice flowers. Responding, “What’s an ice flower?” he quickly led me out to the gardens behind the Totten Center to show me several. Wow, another first-time experience. Then another staff person described an article about ice flowers in the Botanical Garden Newsletter of Nov. -Dec. 2006.

That article, “One Flower You’ll Never Find in the Herbarium,” was written by Carol Ann McCormick, assistant curator of the UNC Herbarium. Though you may never discover one of these ice flowers on your own, I hope, like me, you will be happy to at least know they exist.

With permission, I am sharing here an abbreviated version of Carol Ann’s article.

“The UNC Herbarium is a research collection of 750,000 pressed and dried plant specimens. An herbarium specimen, if a wildflower, is the entire plant, glued and sewn onto stiff, acid-free, 11 ½ x 16 ½ inch paper. If a tree, then a twig with leaves and flowers is mounted on the paper. Bulky items like pine cones or black walnuts are kept in acid-free cardboard boxes.

“Ice flowers, as you will learn, are never found in herbaria.

“I first encountered ice flowers several years ago along my driveway in Alamance County. One cold December morning, I was peeved to see Styrofoam packing peanuts scattered along a rocky east-facing bank uphill from Big Branch Creek. I got out to clean up the litter and discovered that they were not Styrofoam, but delicate whorls of ice. Even more amazing, each whorl of ice was around the base of only one kind of plant, wild oregano, Cunila origanoides. There were plenty of other plants on the rocky bank, Christmas ferns, goldenrods, and melic grass, but ice whorls only at the base of wild oregano.

“A little research revealed that I’m not the first to observe ice flowers. Ice flowers are delicate ribbons of ice that encircle the stems of certain plants when the temperature falls below freezing. According to Forrest Mims (, the flowers ‘are formed when liquid water inside freezes and splits the stem open. Water and water vapor inside the stem are emitted directly into the air, and transformed into delicate ribbons of ice.’

“Ice flowers do not form on just any plant. I’ve found no explanation for ice forming on some plants and not on others. The plant best-known for forming ice flowers is frostweed, Crocanthemum canadense, in the Rockrose family. Verbesina virginica, white crownbeard, and Verbesina alternifolia, wingstem, both in the Aster Family, also form ice flowers. My ice flower plant, wild oregano, is in the Mint family.

“How big are ice flowers? I mistook the smallest ones for packing peanuts, but the largest were fist-sized. When do ice flowers form? I first noted them in a cold spell in mid-December. On a walk at 8:30 p.m., I shone a flashlight beam on the rocky bank, and tiny whorls of ice were beginning to form. How long do ice flowers persist? Once the morning sun heats the forest floor, 8:30 a.m. on this particular slope, the delicate whorls melt away. Where do ice flowers form? The only place I’ve seen them form in my forest is along a 50-foot stretch of my driveway where wild oregano flourishes. I must point out that I am not typically hiking at 7 a.m. on January mornings, so perhaps they occur on other plants! At a meeting of Garden staff last January, I asked if anyone else had noted ice flowers. Most people admitted they’d never heard of, much less seen, the phenomenon.

Every ice flower design is unique. Photo by Patrick Coin.

“I noted ice flowers frequently in December and early January but not afterward. I hypothesize that as winter progressed, the wild oregano stems dried out, so less water and sap was available for freezing. Clearly I have many more questions than answers about ice flowers, but I urge you to be on the lookout for these ephemeral, never to be found in herbaria, ice flowers.”

Thank you to Carol Ann for sharing her observations of these seldom-seen phenomena and to Patrick Coin for the beautiful images.

Comments are closed.