I'm new to this site and I'm looking for information on smaller to medium trees that could be planted within 15-20 feet of a new swimming pool (concrete). I live in the north Las Vegas valley so they need to be drought tolerant even though they will be irrigated by a drip system. I'm most concerned about the roots damaging the walls of my swimming pool as they grow in the years to come. I visited a large tree nursery here in the valley and bought a Sisoo tree and a Japanese privet trained as a tree (single trunk), and three smaller Piru Queen palms. When I did more research on the Sisoo tree, I found that it has invasive roots so I will be changing that selection, even though I really like the looks of it. I need to know if the Japanese privet tree has the same root activity. I really like the fruitless, multi-trunked olive trees (Wilson's) I see on parking strips around here but don't know much about them as far as root activity, mature size, or litter...thoughts? I'm more concerned about the roots than any flowers etc. because they won't be hanging over the pool but I would like something evergreen.
Also, any recommendations as to other plants which would be good neighbors to my pool would be appreciated, over and above sage/yucca, etc.