Pinus ayacahuite, as described in 1838 by Christian Gottfried Ehrenberg (1795–1876) ex Diederich Franz Leonhard von Schlechtendal (1794–1866), in Linnaea 12, is commonly known as Ayacahuite pine or Mexican white pine in the English language. In other languages, Ayacahuite or ayaucuáhuitl in native Nahuatl. In Spanish dialects in regions of Mexico — as a´cxua´t in Totonaca, in Puebla; as acalocote in Puebla; as acalocahuite in Veracruz; as pino cahuite in Hidalgo; as ocote blanco or pino real in Oaxaca; and as ocote gretado, pinabete, pino tabla in Chiapas.
The scientific name is derived from an Aztec name for the tree that honors its stature and habitat, ayauhquahuitl, or "cloud tree." The 16th century monk, Bernardino de Sahagun, described it in his History of the Things of New Spain. He wrote (in Aztec), "it stands towering, highest of all."
Ethnobotany. This species provides one of the most important and sought-after softwoods of Mexico. Formerly very large trees were common, yielding large volumes of an attractive, easily worked timber that provided the raw material for furniture and finish carpentry throughout the country. Those great stands have been largely depleted now, especially in southern Mexico and Mesoamerica
Description. Mexican white pine is an evergreen coniferous species of tree that grows to mature heights of 150 feet (45 m) tall with a 6 foot (200 cm) wide, straight, round trunk, measured at breast height. The tree's crown is pyramidal to conical in shape with regular branch whorls, becoming more irregular and open in old trees.
Bark is thin, smooth, and ash-gray on young trees, becoming rough, gray-brown with age, dividing into small rectangular plates. Wood is soft, creamy white in color, lightweight, and not very resinous.
Branches are long, slender, and horizontally spreading; lower branches often droop.
Twigs are slender, smooth, light gray in color with foliage grouped toward the end.
Leaves (needles) grow in bundles of 5 per fascicle (very rarely 6). They are slender and flexible, measuring 4 to 6 inches (10 - 15) cm long and 0.028 to 0.04 inch (0.7 - 1.0 mm) wide, straight or slightly twisted, flexible but not drooping. Their abaxial surfaces are bright green, adaxial surfaces glaucous with stomata, serrate leaf margins have minute, widely spaced teeth. Stomata appear only on ventral surfaces. Fascicle sheaths are 0.4 inch (20 mm) long, pale brown in color and shed early.
Pollen cones grow crowded at ends of new shoots, are ovoid to short cylindrically shaped, and measure 0.28 to 0.4 inch (7 - 10 mm) long. They are yellow when young, turning orange-brown with age. Pollen dispersal in south-central Mexico typically takes place in May.
Seed cones are also borne near ends of main branches, usually in whorls of 2 to 4, growing on a 1 inch (25 mm) long peduncle that falls with the pendent, slightly curved, almost cylindrical cone. It tapers toward the apex and measures 6 to 16 inches (15 - 40 cm) long and 2.8 to 6 inches (7 - 15 cm) wide when mature and open. They are colored yellow-brown, and quite resinous; ripening in the fall and soon deciduous.
Seed scales number 100 to 150 per cone. They are generally reflexed and curled, thin, narrow, flexible, 2 to 2.5 inches (5 - 7 cm) long, with elongate apophyses, and rounded to obtuse apices. Umbos are to terminal to the scale, lacking a prickle and nearly always resinous.
Seeds are borne 2 per scale, colored light brown with dark spots. They measure 0.32 to 0.4 inch (8 - 10 mm) long and 0.24 to 0.32 inch (6 - 8 mm) wide with an adnate wing 0.8 to 1.4 inches (20 - 35 mm) long and 0.32 to 0.48 inch (8 - 12 mm).
Distribution. This species is native to Mexico — the states of Veracruz, Puebla, Hidalgo, Tlaxcala, Guerrero, Oaxaca, and Chiapas; also native to Guatemala, El Salvador and Honduras. P. ayacahuite typically grows as an emergent tree in mixed stands with other pines, and firs, at elevations of 6,500 to 10,000 feet (2,000 - 3,200 m) above sea level. It grows best on well-drained moist loamy soils on relatively cool, moist sites, such as in riparian areas.
Hardy to USDA Zone 7 — cold hardiness limit between 0° and 10°F (-17.7° and -12.2°C).