Polyalthia longifolia, False Ashoka, Indian Mast Tree
I live in the Middle East (Oman) and wish to plant a privacy screen on my property border. Because I don't want to lose much space in my own yard, I am considering to plants Ashoka (I think the one we have here is known as Polyalthia longifolia, False Ashoka, Indian Mast Tree (see pic which I copied off the web).
Can anyone help to explain the root system of this tree. The information I got is that I can plant this tree with spacing of 3-5 feet. I plan to plant them with 4feet spacing and no more than 3 feet from the boundary wall. Because I want to keep them so close to the boundary, I want to know whether the root system is invasive or whether it will be ok to have them this close.