About Cupressus arizonica var. glabra (Sudw.) Little
This entry covers the tree, scientifically classified as Cupressus arizonica var. glabra (Sudw.) Little and also referred to as Hesperocyparis arizonica. Hesperocyparis arizonica is a coniferous evergreen tree with a crown shaped from conic to ovoid-conic. It reaches heights of 10–25 m (33–82 ft), and its trunk diameter can grow up to 55 cm (22 in). Foliage grows in dense sprays, and ranges in color from dull gray-green to bright glaucous blue-green. The leaves are scale-like, 2–5 mm long, and grow on rounded, not flattened, shoots. Seed cones are globose to oblong, 15–33 mm long, with 6 or 8 scales, rarely 4 or 10. They start out green, and mature to gray or gray-brown roughly 20–24 months after pollination. The cones stay closed for many years, and only open after the branch they grow on is killed, such as during a wildfire or another event. This allows seeds to colonize the bare ground exposed by the fire. Male cones are 3–5 mm 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 is also found in small areas of the southwestern United States, in the southern parts of Arizona, New Mexico, and Texas. In the United States, it grows at elevations between 1,000–1,500 m (3,000–5,000 ft), while in Mexico it can grow as high as 2,200 m (7,200 ft) in some forests. In the wild, this species is most often found in small, scattered populations, not in large continuous forests. One documented location is within 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, the common name for this tree, 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 regions where this disease is common. The cultivar 'Pyramidalis' has received the Royal Horticultural Society's Award of Garden Merit, confirmed in 2017.
