Answer: Most perennials flower for only 3-4 weeks at their peak so if you want year around color, you'll want to plant lots of different plants in your planter. Here are the best performers for hot summer places such as yours:
Kallstroemia grandiflora (Arizona Poppy), grows to about 3' tall and blooms off and on all summer long.
Machaeranthera gracilis (yellow spiny daisy), grows about 1' tall.
Abronia villosa (Desert Sand Verbena), about 4" tall and 20" wide, flowers June-Oct.
Platystemon californicus (Creamcups, Cream Cups), about 1' tall, flowers Mar-May.
Verbena gooddingii (Desert Verbena), blooms Feb-Oct, grows about 1' tall.
Orthocarpus purpurascens (Owl Clover), grows about 16", blooms Mar-May.
Mohavea confertiflora (Ghost flower), 12" tall, blooms Feb-Apr.
Eschscholzia mexicana (Mexican Gold Poppy) flowers Mar-Jun, about 10" tall.
Lupinus sparsiflorus (Lupine), flowers Jan-May, about 2' tall.
Salvia columbariae (Chia), about 20" tall, flowers Mar-Jun.
There are many more suitable plants; visit your local garden center and look for native plants. They will be hardy in your climate and drought resistant.
Best wishes with your garden!
Q&A Library Searching Tips