Johannis pine, dwarf piñon; piñon, piñonero [Spanish].
Syn: P. culminicola var. johannis (R-P.) Silba 1985 (Farjon & Styles 1997).
The validity of this taxon is disputed; Farjon and Styles (1997) regard it as synonymous with P. cembroides var. bicolor (=P. discolor), but Perry (1991), Price et al. (1998), and M.P. Frankis (e-mail 1998.12.20) regard it as a valid species, and after having viewed it alongside of P. cembroides in the field, I agree. This view is also supported by the discovery that this is the only dioecious pine species (Flores-Rentería et al. 2013).
An intermediate view is taken by Passini (1994), who treats P. discolor as a synonym of P. johannis. P. discolor is clearly very close to this species but does differ slightly, and might best be treated as a variety of it. The combination Pinus johannis var. bicolor has however yet to be formally published. The view of Silba (1985) that it is a variety of P. culminicola has some merit in showing that it is more closely related to P. culminicola than it is to P. cembroides, a fact subsequently demonstrated by Malusa (1992) in a very detailed study, but there is no evidence for hybridisation between them where they are sympatric (M.P. Frankis, pers. obs.), and Silba's treatment is rejected here.
Dioecious (the only dioecious pine; Flores-Rentería et al. 2013) shrub or tree, 2-3(4) m tall, multi-stemmed, rarely with a single trunk. Crown low, dense and rounded, spreading, with branches extending outward as much as 3-4 m. Bark in young trees smooth and gray; in older trees rough and scaly, but not deeply furrowed or ridged. Twigs dark gray, rough, the bases of the leaf bracts somewhat decurrent. Leaves (2-)3(-4) per fascicle, 3-5 cm long, 0.9-1.2 mm thick; flexible, margins entire, stomata present only on the ventral surfaces, with a distinctive variegated appearance because the dorsal surface is dark green and the ventral surfaces glaucous white. Resin canals 2, external, dorsal; vascular bundle single. Fascicle sheaths orange-brown, 3 mm long, fading gray, and curled backward into a rosette; later occasionally deciduous. Cotyledons (6-)9(-11). Seed cones in first year brown, 9-11 × 5-7 mm, borne singly or in pairs on short slender peduncles. Cones at maturity chestnut brown, resinous, oblong, 3-4(-4.5) × 2-3 cm when closed, 4-5.5 cm wide when open, opening at maturity and soon deciduous. The peduncle is 3-4 mm long, falling with the cone. Cone scales are thin and stiff, the apophyses irregularly rhomboid, small, thin, flat or slightly raised, 10-15 mm wide, with a weak transverse ridge; umbo dorsal, depressed, the prickle minute and soon deciduous. Only the central (3-)8-15 scales are seed-bearing, those at the base and apex of the cone generally very small and sterile. Seeds dark orange-brown with a rudimentary 0.5-1 mm wing that remains in the cone after seed release; about 11-14 × 10 mm, the seed coat or shell 0.5-1.0 mm thick, hard; about 2,200 seeds/kg; endosperm white; edible. Wood pale yellowish brown, used only for fuel (Perry 1991, M.P. Frankis field notes, NE Mexico 1991.11).
Mexico: Scattered in the higher ranges of W Coahuila, Nuevo León and Zacatecas at 1700-2800 m altitude (Perry 1991; M.P. Frankis field notes, NE Mexico Nov 1991; Farjon & Styles 1997). The type locality is "only in a very limited area near the towns of Concepción del Oro and Mazapil, state of Zacatecas. More recently a number of small populations have been reported in western Coahuila and in the area between the towns of Miquihuana and Aramberri, Nuevo León... In Nuevo León they were growing with P. nelsoni at about 2,800 m" (Perry 1991). Perry (1991) describes the Concepción del Oro stand as occurring at 2,700 m on a steep slope of practically bare limestone, in the company of P. cembroides. The area has 300-400 mm annual precipitation and average annual temperature of 16°C. Frosts are common during December and January. Hardy to Zone 8 (cold hardiness limit between -12.1°C and -6.7°C) (Bannister and Neuner 2001).
Because they do not regard this as a valid species, the IUCN has not classified it as a sensitive taxon. It certainly warrants such classification due to its rarity, its uniqueness, and its vulnerability to exploitation and habitat loss associated with development activity.
The tallest seen by M.P. Frankis (field notes, 1991.11) in NE Mexico was about 4 m tall, on a single erect stem about 15-20 cm dbh, beside a dirt road on the west slope of Cerro Peña Nevada, 23°49'N 99°53'W, at 2680 m altitude (M.P.Frankis 179, 15 Nov 1991 [cited in error in (Farjon and Styles 1997) as at 3500 m]). Most were 2-3.5 m tall, not erect, and branched close to the base, similar to P. culminicola. Trees in the stand that I visited, shown in photographs at left, were about the same size.
Probably not long-lived; no thick stems nor any other indication of great age seen (M.P. Frankis field notes, NE Mexico 1991.11).
"The branches of this small piñon are occasionally used for firewood and the seeds are collected for food" (Perry 1991).
With its very attractive blue-green foliage, it is potentially a valuable slow-growing ornamental species for small gardens in arid areas, but it is scarcely in cultivation yet. USDA hardiness zone 8.
The type locale "is not difficult to find by following Mexico Highway 54 south from Saltillo for about 112 km. Look for a turn off on the right to Concepción del Oro. The road is paved to Concepción del Oro (about 3 km), but from there to Mazapil it is narrow, steep and unpaved. Though the pines can be found only a few kilometers from Concepción del Oro, it would be best to plan collections during the dry winter months, November-February" (Perry 1991).
It can also be seen scattered in the high valleys between San Antonio de las Alanzas and Monterrey around the Nuevo León / Coahuila border; these populations have only been discovered in recent years and are not mapped by Perry (1991), but are shown by Farjon and Styles (1997). At some of these sites it is separated from populations of P. culminicola by under 5 km and 400 m of altitude; despite this close proximity, no hybrids have been observed between these closely related taxa. Throughout its range, it also often occurs intimately mixed with P. cembroides, but again, no evidence of hybridisation has been found.
P. johannis was named after Mlle. Robert's fiancé, Johann Passini, whom she later married; she published subsequent papers first as M.-F. Robert-Passini and then as M.-F. Passini.
Flores-Rentería, Lluvia, F. Molina-Freaner, A.V. Whipple, C.A. Gehring, and C.A. Domínguez. 2013. Sexual stability in the nearly dioecious Pinus johannis (Pinaceae). American Journal of Botany 100(3):602–612. doi:10.3732/ajb.1200068.
Robert, M.-F. 1978. Une nouveau pin pignon Mexicain: Pinus johannis. Adansonia ser. 2, 18:365-373.
Much of this page was prepared by M.P. Frankis, 1999.02.
Last Modified 2013-06-20