How often should I water newly planted Japanese boxwoods living in the High Desert?

Hi! kathyann6, and welcome to AMHD :)

Go to:
Arizona Master Gardener Manual (http://ag.arizona.edu/pubs/garden/mg/)

Then left side click on Arboriculture.
Scroll down to Watering Plants.

This one in North Carolina
Growing Boxwoods in the Landscape (http://www.ces.ncsu.edu/depts/hort/hil/hil-8628.html)

K