About Cupressus arizonica var. nevadensis (Abrams) Little
This entry addresses Hesperocyparis arizonica, previously classified as Cupressus arizonica var. nevadensis (Abrams) Little. Hesperocyparis arizonica is a coniferous evergreen tree with a crown that ranges from conic to ovoid-conic in shape. It reaches heights of 10 to 25 meters (33 to 82 feet), and its trunk can grow up to 55 centimeters (22 inches) in diameter. Its foliage grows in dense sprays, and ranges in color from dull gray-green to bright glaucous blue-green. The leaves are scale-like, 2 to 5 millimeters long, and grow on rounded shoots, not flattened ones. Seed cones of this species are globose to oblong, 15 to 33 millimeters long, and have 6 or 8 scales, rarely 4 or 10. The cones are green when young, and mature to gray or gray-brown roughly 20 to 24 months after pollination. These cones remain closed for many years, only opening after the branch they grow on is killed, such as during a wildfire or other event. This allows the seeds to colonize the bare ground left exposed by fire. Male cones are 3 to 5 millimeters long, and release pollen between February and March. Hesperocyparis arizonica occurs mainly in northern Mexico, in the states of Chihuahua, Coahuila, Durango, Tamaulipas, and Zacatecas. It also grows in small areas of the southwestern United States, in the southern regions of Arizona, New Mexico, and Texas. In the United States, it grows at elevations between 1,000 and 1,500 meters (3,000 to 5,000 feet), while in Mexico it can reach up to 2,200 meters (7,200 feet) in some forests. In the wild, this species most often occurs in small, scattered populations rather than large continuous forests. One documented location is in the Sierra Juárez and San Pedro Mártir pine–oak forests of Mexico, where it grows alongside canyon live oak and California fan palm. Arizona cypress is widely cultivated as an ornamental tree. Unlike Monterey cypress, it is highly resistant to cypress canker, a disease caused by the fungus Seiridium cardinale, and grows reliably in areas where this disease is common. The cultivar 'Pyramidalis' has earned the Royal Horticultural Society's Award of Garden Merit, a confirmation of this award issued in 2017.
