Frostflowers are neither frost nor flower, but are “blooming” right now.
They happen when air temperature drops below freezing and warmer groundwater rises to extrude itself through the convenient conduit of a real flower stem, especially if that stem is a white crownbeard (Verbesina virginica). The water freezes on contact with air, and fresh waves push older crystals forward and out. Crownbeard’s winged structure aids the process. Other species can produce frostflowers, but white crownbeard is such a common enabler that the plant’s most common common name is frostweed.
Apparently, frost flowers are not made of frost. A more accurate term would be iceflower. “Ice segregation” is the process at work, and should you wish a detailed explanation, read My World of Ice online by Dr. James R. Carter, Professor Emeritus of Geography-Geology, Illinois State University.
For photos of the real flowers of white crownbeard (which are white!) see this entry at my friend Gail’s native gardening blog, Clay and Limestone. The plant is lovely, native, and an important nectar source for insects (including Monarch butterflies), and “the foliage is a larval host plant for the Summer Azure, Bordered Patch, and Silvery Checkerspot butterflies.” (source)
Almost as easy as growing frostflowers.