Not quite freezing, but cold enough
When I checked the outside thermometer yesterday morning at around 5:30, it read 38°F (3°C): not quite freezing but cold enough, I verified a few hours later in Great Hills Park, for frostweed (Verbesina virginica) to have done its ice trick overnight. Only a few plants were involved, and the formations fell short of the best and biggest ones I’ve seen, but at least we finally had a bit of icy delicacy in what has so far been a winter without a winter. If you’re new to this phenomenon, the next paragraph is a version of the explanation I gave in previous years.
The name frostweed comes from one of the strangest phenomena in botany. By the time the first freeze settles in overnight on the lands where this species grows, almost all of these plants have gone to seed. Although each stalk stands there dried out and unappealing, that first frigid touch can cause it to draw underground water up into its base. Now for the bizarre part: the section of the stalk immediately above the ground splits open as it extrudes freezing water laterally, and the process produces fragile sheets of ice that curl and fold around the broken stalk or even unscroll away from it.
Here’s a closer look at some of those little icy scrolls I photographed yesterday:
If you’d like to see views of frostweed ice from former years, here are a few:
© 2016 Steven Schwartzman