Pinus strobiformis

Engelmann 1848

Common names

Mexican white pine, southwestern white pine (Elias 1987), pino blanco, pinabete (Perry 1991), pino enano (Kral 1993).

Taxonomic notes

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.

Description

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).

Range

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). See also Thompson et al. (1999).

Big tree

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.

Oldest

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).

Dendrochronology

Ethnobotany

The seeds were eaten by natives of the southwest U.S. (Little 1980). It is locally (in Mexico) used for cabinetry, doors and window frames (Perry 1991).

Observations

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:

• In mixed pine forests near 3,500 m elevation, at about 25.3333°N, 100.5000°W.
• At about 2,000 to 3,500 m elevation on Cerro Potosí, at about 24° 50' N, 100° 15' W. I have been to this site, where it grows with P. culminicola, P. hartwegii, and P. arizonica var. stormiae. See the Taxonomic Notes section of P. flexilis for remarks on P. strobiformis × flexilis hybrids that can be found here.
• Near Madera in Chihuahua, on north slopes at 2,000 to 3,500 m elevation, at about 29.2°N, 108.45°W. For this site you will need a local guide, a high-clearance vehicle, and should only go during the dry season.

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!

Remarks

White pine blister rust. (Cronartium ribicola), an introduced fungal disease, attacks this and certain other white pines (Little 1980).

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).

Citations

See also

FEIS database.

Burns and Honkala (1990).