Mexican white pine, Chihuahuan white pine, southwestern white pine; pino blanco, pinabete, pino enano [Spanish].
Syn: Pinus ayacahuite Ehrenberg var. brachyptera G.R. Shaw; P. ayacahuite var. reflexa (Engelmann) Voss; P. ayacahuite var. strobiformis (Engelmann) Lemmon (Kral 1993). See below.
This is a typical white pine in section Strobus, subsection strobi. This species is closely related to Pinus flexilis, with which it forms the hybrid Pinus flexilis var. reflexa (Farjon and Styles 1997).
In 2008, Michael Frankis described a new species, Pinus stylesii Frankis ex Businský, from Cerro Potosí and neighboring mountain ranges, chiefly in Nuevo León, Mexico. I believe that this taxon is derived from the hybridization of P. strobiformis and P. flexilis, and have reduced it to synonymy with Pinus flexilis var. reflexa, although in actuality it probably lies somewhere between typical P. flexilis var. reflexa and typical P. strobiformis. The full story is given on the P. flexilis page.
Trees to 15-24(30) m tall and 50-90 cm diameter, slender, straight; crown conic, becoming rounded to irregular. Bark smooth and silvery gray on young trees, aging to a dark grayish brown, furrowed, divided into rough rectangular plates. Branches spreading-ascending; twigs slender, pale red-brown, puberulous or glabrous, sometimes glaucous, aging gray or gray-brown, smooth. Buds ellipsoid, red-brown, ca. 1 cm, resinous. Needles 5 per fascicle, spreading to ascending-upcurved, persisting 3-5 years, 4-10 cm × 0.6-1 mm, straight, slightly twisted, pliant, dark green to blue-green, abaxial surface without evident stomatal lines, adaxial surfaces conspicuously whitened by narrow stomatal lines, margins sharp, razorlike and entire to finely serrulate, apex narrowly acute to short-subulate, resin canals 2-4, external; sheath 1.5-2 cm, shed early. Staminate cones cylindric, ca. 6-10 mm, pale yellow-brown. Ovulate cones maturing in 2 years, shedding seeds and falling soon thereafter, pendent, symmetric, lance-cylindric before opening, broadly lance-cylindric when open, 15-25 cm, creamy brown to light yellow-brown, stalks to 6 cm; apophyses somewhat thickened, strongly cross-keeled, tip reflexed; umbo terminal, low. Seeds ovoid; body 10-13 mm, red-brown, essentially wingless. 2n=24 (Little 1980, Perry 1991, Kral 1993).
US: Arizona, New Mexico, Texas; Mexico: Coahuila, Nuevo León, Sonora, Chihuahua, Sinaloa, Durango; at 1900-3000 m. Habitat dry rocky slopes in high mountains, or as a minor component in mixed conifer forests. In the United States such habitat occurs on isolated desert mountain ranges, and in Mexico it is widespread in both the Sierra Madre Occidental and Oriental. Within habitat, it mostly grows on moist, cool sites with associates such as P. hartwegii, and P. culminicola (Little 1980, Perry 1991, Kral 1993). Hardy to Zone 8 (cold hardiness limit between -12.1°C and -6.7°C) (Bannister and Neuner 2001). See also Thompson et al. (1999).
In the United States: diameter 150 cm, height 34 m, crown spread 19 m, located in Lincoln National Forest, NM (American Forests 1996). Since the great majority of the species' range is in Mexico, larger trees may be found there.
Tree VPK02 collected in the San Mateo Mountains of New Mexico by Henri Grissino-Mayer, J. Speer, and K. Morino had a crossdated age of 599 years (RMTRR 2006).
In the United States, it can be found near the summits of the Chiricahua Mountains and probably in other high ranges of southern Arizona. In Mexico, Perry (1991) recommends the following locations:
As referenced in the photos at left, I have also found fine occurrences of it in the high passes on Mex-16 between Hermosillo and Chihuahua and in Durango about 20 km S of the town of El Salto. No guides or fancy vehicles needed for these sites!
This species is the primary hosts for the dwarf mistletoe Arceuthobium blumeri, which extends from southern Arizona south through Durango and east to Cerro Potosí in Nuevo León (Hawksworth and Wiens 1996).
Engelmann 1848. Sketch of the botany of Dr. Wislizenius' expedition. Appendix, pp. 87-115, to Wislizenus, F. A. Memoir of a Tour to Northern Mexico. Washington.
Last Modified 2012-11-23