This winter, when conditions are just right—that is to say, the ground is not frozen but the air is—you might see papery white blossoms unfurling from long-stemmed plants. These "frost flowers" don't fall into any taxonomic category per se, but their sightings are as enthusiastically documented as any rare orchid. Or, perhaps more appropriately, a rainbow. The phenomenon occurs when sap in the stem of a plant expands, casting long, thin cracks along the length of the stem. Capillary action draws water through the cracks, which freezes upon contact with the air, and the thin layers of ice ribbon like frosting. They're quick to melt, so look for them in the early morning in shaded areas.
Plants that commonly form frost flowers are White crownbeard (Verbesina virginica), Yellow ironweed (Verbesina alternifolia), American dittany (Cunila origanoides) and Helianthemum canadense.
Photo credit: Dean Morris
Photo credit: Nick Page
Photo credit: MarkInspex / Flickr