Are Box Bushes Good for Arizona?

From Snow to Glow

• Located in the U.S. Southwest on the Mexican border, Arizona goes from mountainous northern areas with peaks as high as 12,633 feet near Flagstaff to Yuma in the south at 138 feet above sea level. Climate is influenced by rain shadows in the west, moisture from the Gulf of California in the south, and high elevations of the Rocky Mountains and Colorado Plateau to the north. The state's U.S. Department of Agriculture (USDA) plant hardiness zones go from 4b on mountaintops to 10b along the Colorado River. Southwestern Arizona belongs to the hot Sonoran Desert.

In the Desert

• Japanese boxwood (Buxus microphylla japonica) will grow in the desert. In order to grow well in heat and low humidity, however, it needs regular watering -- every week or more often in summer -- and partial to full shade, preferably an eastern or northern exposure. The bush has a slow to moderate growth rate and reaches 4 to 6 feet tall. It produces upright, dense growth and displays inconspicuous greenish flowers in spring. It is hardy in USDA zones 7 through 11 and can be hardy in protected locations in USDA zone 6. Japanese boxwood cultivars include "Winter Gem," "Green Beauty" and "Compacta." In desert areas, Japanese boxwood is suited best to mesic, shaded plantings for low-maintenance hedges, edgings or accent plants.

  English boxwood (Buxus sempervirens) and Korean boxwood (Buxus microphylla koreana) aren't good desert subjects.

In Mid-Elevation Regions

• Mid-elevation areas between 3,500 and 5,000 feet include the chaparral zone and high-altitude desert. Summers are hot and dry, winters are cool and average annual rainfall is 15 to 24 inches, with 55 percent falling in winter and 45 percent occurring in summer. An example of such an area is Globe, Arizona, which is in USDA zone 9a and has an average annual rainfall of 19 inches. Japanese boxwood grows well at the 3,500- to 5,000-foot altitudes, which have double or triple the average annual rainfall of Sonoran Desert areas. English boxwood is at the upper limit of its USDA zone range of 5 through 8 in mid-elevation areas and doesn't do as well as Japanese boxwood in those regions of Arizona.

In Higher Elevations

• At Arizona's elevations where pine forests naturally occur, such as Flagstaff in USDA zone 6b, and Prescott and Payson, both in USDA zone 7b, the more cold-tolerant Korean boxwood grows well. It is hardy in USDA zones 5 through 9. Some Korean boxwood varieties may turn yellow-brown to purple in winter, but the cultivar "Wintergreen" retains greener winter vegetation. Korean boxwood grows 3 to 4 feet high and wide and has a naturally rounded shape. Protect the bush from drying winds in winter and from sun scald. The tidy, slow-growing plant needs little maintenance if it is allowed to grow naturally, but a sheared plant needs more maintenance. If you want a plant with more cold hardiness and suitable for an area such as the White Mountains, then consider the hybrid cultivar "Green Gem" (Buxus microphylla var. koreana x Buxus sempervirens), which is hardy in USDA zones 4 through 9.