Vitex trees, also called monk's pepper or chaste tree, grows 10 to 15 feet tall and 15 to 20 feet wide. In Arizona it blooms in late spring with pointing lavender flowers. This plant is hardy in USDA zones 7 to 11; it grows where the temperature does not drop below 0 degrees Fahrenheit. Vitex trees can grow throughout Arizona except in the coldest regions in the northeast.
Plant the vitex tree in full sun or part shade and loose, well-drained soil. This plant can survive hot weather and likes somewhat dry soil. In the cooler regions of northeastern Arizona plant the more hardy vitex negundo instead of vitex agnus.
Water the vitex deeply every seven to 10 days in hot, dry weather. In cooler times, once or twice a month is sufficient for the tree to thrive in Arizona. The plant will survive without supplemental water but grows faster and healthier with it.
Prune the vitex in late winter or early spring with pruning shears. You can prune this plant either to shrub form or tree form. For shrub form, cut the bush down to the ground annually. For tree form, prune the branches away from the bottom of the trunk. In both cases, cut out weak or broken branches, branches that rub and any suckers coming off the base of the trunk.
Fertilize the vitex tree each spring with a complete, all-purpose fertilizer marked 10-10-10. This will provide enough nutrients for the plant in Arizona soil. Follow the directions on the package for application instructions. Each brand of fertilizer will have different instructions.