Not a plant, but explanation sought...

[Gail]

Pictures show an ice phenomenon which formed in a friend's bird bath (shallow ceramic plant saucer). There are no trees or anything above so this is not the result of something dripping from above. My friend is a sculptor, so my explanation was that the water had been watching her work through the studio window and wanted to do something equally creative but a more scientific explanation would be good from one of our more knowledgeable members!

[Alan_b]

Ice floats on water.  So imagine if a little drop of ice, a hailstone, were to land on a bowl of water that was just above freezing point when the air temperature was just below freezing.  The ice might blown around in the wind and act as a seed crystal so water from the bowl would freeze on the surface of the ice and the drop of ice would get larger, until such time as the surface water in the bowl freezes over also.  I don't know if this is really what happened but it seems plausible. 

[Maggi Young]

Fascinating - and rather beautiful  phenomenon.

 More about  nice ice  here : http://my.ilstu.edu/~jrcarter/ice/radio/

It seems these  "growths" are called "Ice Spikes"  and occur when the temperature drops suddenly....
https://en.wikipedia.org/wiki/Ice_spike

[Gail]

Thank you both - those links are amazing Maggi!

[Maggi Young]

I thought so, Gail. You are so lucky to have seen and photographed this!

[ashley]

Fascinating.  Always learning here on the forum

[Rick R.]

I didn't know about any of these phenomena, until last fall, and even then I was baffled.  It was interesting that this only occurred on the two iris I had cut back in late fall.  The rest of the garden only had just a little bit of regular hoar frost, and nothing else was cut so close to the ground.