Answer: The University of Arizona Cooperative Extension has a great free pub on Frost Protection you can download at the following site. Look under Weather and Frost Protection for AZ 1002.
As for the best time to plant, probably in late winter/early spring after the last frost date in your area to give it time to establish root system before going into the summer heat. Mimosa does like the heat so it will grow during the summer, but will need careful watering. Alternatively, plant in late summer/early fall before the first frost date. That's usually a less-stressful time to plant, but as you know, be careful about frost. Good luck!
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