Portraits of Wildflowers

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Archive for December 12th, 2012

Frostweed debuts its ice trick for 2012

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Frostweed Ice 1594

If you don’t recall or don’t know what Verbesina virginica looks like when it’s fresh, you may want to take a quick look back at a picture from this summer. As for the origin of the vernacular name frostweed, let me repeat what I wrote at the end of November last year. The common name for this species comes from one of the strangest phenomena in botany. By the time the frost begins settling overnight on the lands where frostweed grows, almost all of these plants have gone to seed. Although each stalk stands there unappealingly as it dries out, the first good freeze can cause it to draw underground water up into its base. Now for the strange trick: the exterior of the part of the stalk near the ground splits open as it extrudes freezing water laterally, and that process produces thin sheets of ice that curl and fold around the broken stalk and sometimes even unscroll away from it (you can see that unscrolling in a photograph from last year).

I took this picture of the fabled frostweed phenomenon yesterday morning in Great Hills Park. The sun had already been climbing for a couple of hours, and as its light reached the frostweed and the temperature rose, the ice began to melt. You can see that the narrow cone of ice that formed the right-hand peak of this formation had come loose from the frostweed stalk and was leaning far enough over that it would soon fall off. The whole left side of the ice already looks partially detached from the stalk as well. In the mild climate of Austin, frostweed ice rarely makes it through the morning, and yesterday was no exception.

To see the many places in the southeastern third of the United States where Verbesina virginica grows, you can consult the state-clickable map at the USDA website.

© 2012 Steven Schwartzman

Written by Steve Schwartzman

December 12, 2012 at 6:19 AM

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