This tree is growing out of my unused compost bins. It's been growing for a few years, and I should probably remove it before it damages the foundations further.
Update: It seems to be growing from the top of the compost bin so the roots may not be a danger after all. It's over 12 foot tall, and can't be more than 2 years old in retrospect. The stem is green all the way from the bottom to the top, and there are no flowers. The leaves alternate on the branches, and their maximum length is about 6 inches. The leaves are not serrated, and are glossy.
I'm in Wellington, New Zealand and the temperature rarely goes below freezing.