Mystery

This really puzzled me when I saw it this morning. It had been a cold night and there was a bit of frost and ice in the garden. I found this icicle particularly pretty and wanted to get some shots of it. 

So what's odd about that? No, not me getting a blip before 11am! The very strange thing is that the icicle is pointing upwards! No, there wasn't water dropping onto it from above. A small wheelbarrow tyre has been lying in the garden and water had collected in the hub, but today there was a very sharp, pointed icicle sticking up 5" out of it. (See Extra) The sort of icicle that could have featured in a murder drama on TV had someone been pushed over onto it!

I took great care not to stumble!

EDIT: Thanks gen2 for the answer to this: Supercooling!