Sunday, January 8, 2012

Frost Flowers

I had a chance this week to find something quite unusual in my yard - frost flowers.  They are not true flowers, and it takes a special event in Georgia to produce them: good moisture in the ground and it's got to get COLD.  I like the explanation in Wikipedia so much that I will paste it here verbatim:

"The formation of frost flowers, also known as "ice flowers," is dependent on a freezing weather condition occurring when the ground is not already frozen. The sap in the stem of the plants will expand (water expands when frozen), causing long, thin cracks to form along the length of the stem. Water is then drawn through these cracks via capillary action and freezes upon contact with the air. As more water is drawn through the cracks it pushes the thin ice layers further from the stem, causing a thin "petal" to form."

Late summer flowers, Cunila origanoides

I learned about this condition only recently by way of a friend in the Georgia Native Plant Society.  She called it "crystallofolia" and provided some pictures of dittany (Cunila origanoides) in her yard exhibiting the condition.  Another friend used those pictures to write an article about it for the January newsletter.  Still - I didn't expect to see it myself.  We've had some warm weather lately but earlier this week it got very cold - below 20 overnight!

After a tip from my friend Jane that she found some in her yard, I went outside to look. Bingo!  My dittany had frost flowers too!

While this oozing, freezing, "flowering" event is very exciting, photographing it is so not easy!  Here is a picture of the frost flowers in my yard:

Cunila origanoides

A much better picture belongs to my friend Jane - she sent me this picture of the frost flowers on her Joe-Pye weed (Eupatorium sp.):

Eupatorium sp.

This subject is a popular topic this week due to the cold snap throughout the eastern U.S. Gail over at the blog Clay and Limestone also has a post on this with some very excellent pictures of Verbesina virginica from Tennessee.


  1. Interesting, I learn something new every day!

  2. First time I'd seen these on Gail's blog. So interesting, do you think it's a southern phenomenon only?

  3. I am not sure, but certainly a lot of the descriptions of it on the web seem to be from southeastern sources.

  4. I have been studying frost flowers for over 10 years. They are common on Verbesina virginica and alternifolia as well as ditany. This is the first example of occurrence on Joe-Pye weed that I have encountered.

    I am starting a more organized effort to collect new species of "host plants" for frost flowers. Please help spread the word and report your results to me at or directly at

    Thanks for your post.

  5. Very nice photo of the frost flower on the dittany! I tried growing dittany one year and enjoyed it as an herb, but it was somehow uprooted and lost. I hope to try it again -- this time from seed!