What is this?

[Queenslander]

This is the top of plant, a little bent over


I am in sub-tropical eastern coast of Australia. Have found in my garden, growing on 2 trees, about 4 feet high, the above, coming out of the ground. Has terete shaped leaves, spiky point, the more water I give it the more aerial roots come out. The one above is a piece I have cut from the main stem. It looks v. healthy, can anyone help with its ID. Is it an orchid? We moved to this house nearly 2 years ago.