Answer: The most important things when choosing plants are determining what sun exposure (full, partial, shady) they will thrive in and how much space they need to grow to maturity (both vertically and horizontally), and then comparing that with what your landscape offers. The 3 foot wide space is a limiting factor in your choices. Although palms don't have extensive root structures I can't think of any that would fit in that 3 foot space. I'd suggest sticking with smaller shrubs, perennials, groundcovers or succulents. There are so many colorful possibilities and since I can't know your likes and dislikes I'm going to provide you with some great resources. First, contact the Phoenix City Water Conservation Department for a free copy of Landscape Plants for the Arizona Desert. It is a color guide listing more than 200 low-water-use plants, along with growing and special characteristics (e.g., hummingbirds, etc.) For appropriate poolside plantings, you want things that can take extreme reflected heat and that don't drop alot of litter to clog the equipment. Download this free publication from the University of Arizona Cooperative Extension: Poolside Plantings, AZ 1058 http://ag.arizona.edu/pubs/garden/az1058.html. It's also available as a PDF.
The narrow space with intense reflected sun and heat you have is a tough growing condition. Try to stick with native and desert-adapted choices, such as those listed in the above publications. They are adapted to our heat, alkaline soil, aridity, sunshine and have few if any pest problems. Good luck!
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