Q: We've just moved to the northern Arizona desert. It's very dry and windy, with freezing nights in the winter. We could really use some hedges, but I'm not sure what to plant. — Clara Soto, Page, Ariz.
A: Stiff wind, scant rainfall, and harsh sunlight are your biggest challenges — not the cold. If you can supply drip irrigation to counter the drying effects of these elements, there are lots of plants to play with. Steer clear of the old standbys — photinia, Japanese boxwood, pyracantha, and privet — that landscapers in your area routinely recommend despite their need for regular pruning and constant watering. Instead, try some of the more adventurous options that your relatively mild winters permit (you’re in USDA cold-hardiness zone 8). Use plants that have naturally adapted to survive long periods in dry soil.
For a strikingly tall, formal hedge, plant the straight and narrow Italian cypress, Cupressus sempervirens ‘Stricta’ or blue-green Glauca’ (USDA zones 7–9), or Rocky Mountain juniper, Juniperus scopulorum ‘Skyrocket,’ ‘Gray Gleam,’ or ‘Blue Haven’ (zones 3–7). All these trees stay dense and columnar without shearing, though they will eventually overshoot the 6- or 8-foot height that most of us have in mind when we think hedge. A wise choice for an informal hedge that’s easy to restrict to the 6- or 8-foot limit is cliff rose, Cowania mexicana (zones 4–7). Shear its sides once a year, and thin out older wood as needed to rejuvenate the plant and control its height. Cliff rose never loses all of its small gray-green leaves, and it is thick with fragrant yellow flowers in spring, followed by sparser yet steady blooms all summer (when it’s trained as a hedge, this native shrub actually blooms more profusely than it does in the wild). The flowers then become attractive plumes. A close relative, Apache-plume, Fallugia paradoxa (zones 3–10), has white flowers and even lusher plumes, though its mature height is about 4 feet.
If you have room for a larger, looser planting — more of a hedgerow than a hedge — Arizona cypress, Cupressus arizonica (zones 6–9), may be just the ticket. This cypress is fairly short for a tree, ultimately about 18 feet across at the base and 25 to 30 feet tall, and it forms a sturdy screen and windbreak. Pinyon pine, Pinus edulis (zones 5–8), which eventually reaches a height of roughly 20 feet, is a fine alternative. Growth is slow: less than 6 inches a year without watering.
During their first 6 months in the ground, all the plants I’ve recommended should be irrigated regularly with a drip line to help them settle in. From then on they will thrive with little supplemental irrigation. Cliff rose and Apache-plume are happiest subsisting on rainfall alone, but the rest of these plants will grow faster with every extra drop you give them.