I first posted about frost flowers a little more than ten years ago on this blog. This season, after learning about the two plants that are most likely to form them in our geography and having the flexibility to be on location at the specific times they are capable of forming, I was able to take advantage and take my time in capturing them with the camera.
The first gallery are the more robust of the crystallofolia. Dave and I stumbled across these in Madison County, MO. These are formed on the dying stalks of Verbesina virginica (F. Asteraceae), aptly named “frostweed” or white crownbeard. This is the more robust plant of the two featured here and, consequently, forms larger and more robust frost flowers. Some of these were up to 12″ in height.
A note about how crystallofolia form.
Because these later-maturing species are still somewhat viable during the first deep freeze, the xylem pathways responsible for moving water from the roots to the shoots are still functional. The roots in the still unfrozen soils are pushing water to the shoot of the plant via capillary action. On the first few nights when temperatures drop to the mid 20 degrees F, the water in the shoot freezes, bursting the sides of the stem pushing the freezing water out and forms these gorgeous petals. If you look closely, you can see the individual “tubes” of ice that make up the petals of the frost flowers. These tubes correspond directly to the xylem rays – the tubes that distribute water from the vertical rising xylem to the outer tissues of the plant. Another interesting thing about these structures is that they will often dissipate through sublimation. The super cold and dry conditions can cause these thin and delicate petals to evaporate directly to gas, skipping the liquid water phase.
The second species featured here were found in Jefferson County, MO on a trail. Earlier in the season I had noted the abundance of dittany (Cunila origanoides) F. Lamiaceae. This species is smaller and forms dainty frost flowers, mostly no more than four inches in height. They can also be much more elaborate than the frost flowers formed by V. virginica, with long, curling petals that have a tendency to curl back on themselves.
A Thousand Acres of Silphiums 