Pinus arizonica / Arizona pine

subgenus Pinus, section Trifoliae (Duhamel), subsection Ponderosae (Louden).

Pinus arizonica, first described in 1878 by Georg Engelmann (1809–1884) ex Rothrock is commonly known as Arizona pine or as pino de Arizona in the Spanish language. In the 1997 monograph, Pinus (Pinaceae) in Flora Neotropica, Aljos Farjon and B.T. Styles state that P. arizonica has often been treated under P. ponderosa as a variety, but more recent treatments recognize it as a distinct species, with possible introgression in Arizona and New Mexico.

artwork courtesy of University of South Florida
artwork courtesy of University of South Florida

Description. Arizona pine is a large growing coniferous species of tree that grows to heights of 112 feet (35 m) tall with a straight, massive trunk up to 48 inches (120 cm) in diameter, measured at breast height. Mature trees present an open crown with a rounded top and thick, spreading branches, while young trees will be more pyramidal in structure.

  • Bark on young trees is dark brown, rough and scaly, with age becoming up to 2 inches (4 - 5 cm) thick, deeply furrowed, and divided into large irregular plates separating into thin, closely appressed light cinnamon-brown scales.
  • Needles grow tufted at the ends of the branches, in fascicles of 3 to 5 needles, 5 to 9 inches (12 - 22 cm) long, thick, rigid, dark green in color, with stomata on all sides; finely serrate margins. Needles tend to fall after 2 to 3 seasons.
  • Seed cones are symmetrical, ovoid to conical shaped, 2.5 to 4 inches (6 - 9 cm) long, born in groups of 1 to 3 on short, stout peduncles They are light red-brown at maturity, with hard, stiff scales 0.48 to 0.56 inch (12 - 14 mm) wide, with a rounded apex, smoothed with apophyses raised and with a transverse keel; armed with slender recurved spines. Cones open at maturity and are soon deciduous, leaving the peduncle and a few basal cone scales attached to the branchlet.
Natural range of <em>Pinus arizonica </em>varieties.
Natural range of Pinus arizonica varieties.

Distribution. This species is native to USA in the mountains of southeastern Arizona and southwestern New Mexico at elevations of 5,800 to 8,000 feet (1,800 to 2,450 m). In Mexico, it is found in the mountains of the Sierra Madre Occidental in northeast Sonora, west Chihuahua, eastern Sinaloa, and Durango at elevations of 6,400 to 9,000 feet (2,000 - 2,800 m) above sea level.

Hardy to USDA Zone 8 — cold hardiness limit between 10 to 20ºF (-12.1°C to -6.7°C).

Attribution from: Aljos Farjon and B.T. Styles; Pinus (Pinaceae). Flora Neotropica Monograph 75; ©New York, NY: The New York Botanical Garden.

Pinus arizonica growing in nature on Mt. Lemmon, Arizona.
Photo by Debbie, via Wikipedia