Update: This is called 'hair ice' and is the result of a fungus that breaks
down dead/dying plant material. (19 January 2025)

Not sure how this happens or what the process may be called but on multiple
stems of a patch of flowers subfreezing temps caused ice to form on their
stems. I have never seen this before anywhere. One thought is possibly
epiphytic ice nucleation active (INA) fungus or bacteria, otherwise
I'm clueless. Okay, okay, on a lot of other things too!