"Nature will find a way."
(Ian Malcolm - Jurassic Park.)
Growing in a 'pipe' bracket I made twenty years ago. I didn't have the heart to remove it.
Hi @Noyade,
It really is incredible where you'll find plants growing. They really do "find a way".
In saying this, that looks like a https://en.wikipedia.org/wiki/Kalanchoe_delagoensis , known as Mother of Millions, which is considered a noxious weed in some parts of Australia.
Have a look at https://weeds.dpi.nsw.gov.au/Weed/Motherofmillions for some further information.
I just did a bit of research and thought I would share. It is likely harmless, but as it reproduces vegetatively, meaning through dropped leaves, it has the potential to spread quite rapidly.
Jacob
"noxious weed"
That's terrible news Jacob! I thought it might be a fern of sorts. I'll let him grow overnight and pluck him tomorrow - when he's not expecting it.
Cheers.