You scared me for a minute. I'm in Las Vegas so when I saw your Ficus mentioned I was concerned. I am less concerned with it in the Phoenix area but the pool area puts it in a different twist and you still have to worry about freezing damage.
But I am going to copy this to my good friend Terry Mikel who was your Extension Specialist in Maricopa County with the main office in Phoenix. He is better at answering this one and I will post his answer. He is in retirement but I am SURE he will come out of hiding on this one!
Q. I live in Glendale Arizona. I have a 45ft section of 6 foot brick wall that I would like to plant Ficus nitida along. There is a 4 foot width between the wall and a plaster underground swimming pool. No problem watering the hedge? But will this plant seek the pool water and cause a problem. I am not worried about frost. I want a 10 foot hedge when done.
A. Your thoughts about having a hedge sound good. Ficus microcarpa sub species/or cultivar 'Nitida' can fit the situation; its clean (no real messes). evergreen and makes a dense wall of foliage.
I have to use the term 'can' with a couple caveats.
1. This plant can grow to a very large size. Frosts every few years help keep them in check. And pruning can, to a certain degree keep them in check. But, frosts and pruning will be a continuous battle against their genetics: it wants to be a 60' tall and 80' wide tree.
2. This species of Ficus will after time develop huge surface roots that will lift, push or barge anything in their path. It’s their genetics and watering will have little, if any affect so the wall to the one side and any pool decking on the other side will be vulnerable to the large lifting roots.
Your one concern about them 'seeking' water is a commonly misunderstood trait of any plant. . . Plants do not search out water, period. Plants send out roots randomly in all directions and roots that run into a water source will proliferate.
Pool sides, if sound will be the same a rock in nature, the roots will try to grow up, under, or around any solid object.
If, and this is a big if there is the slightest oozing leak from the pool's wall and a root meanders there then it will grow and proliferate in response. That's where the issue of roots and pools becomes a problem.
Personally, the Ficus is overused and most people who grow them quickly tire of all the problems with them. If anyone who knew much about them would warn folks against using them except for large evergreen tree.
Your setting is a little bit of a challenge. You might think about something much less vigorous with fewer potential problems and some have blooms (a potential 'mess' issue). Look at: citrus, Hop Seed Bush (Dodonea), Xylosma (both common and botanical name), Arizona Rosewood (or any in that genus of Vauquelinia), one of the many different blooming colors of Arizona Yellow Bells (Tecoma and various species and varieties), Petite Oleanders have been used in that setting for generations.
Every person's 'likes' and 'dislikes' vary. Check with your water department and pick up some of the nice booklets about planning and plants for the landscape. These were produced by the Arizona Municipal Water Users' Association, more lovingly called AMWUA to be distributed in the different communities.
Another resource might be going to the Mountain States Wholesale Nursery (MSWN.com) site for a truly complete list of plants that are well adapted in the lower Sonoran desert. They also produce some for the higher deserts but their main goal is for lower deserts. .
Terry H. Mikel