| Pinus strobiformis | |
|---|---|
 | |
| Pinus strobiformis in Jalisco, Mexico | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Gymnospermae |
| Division: | Pinophyta |
| Class: | Pinopsida |
| Order: | Pinales |
| Family: | Pinaceae |
| Genus: | Pinus |
| Subgenus: | P. subg.Strobus |
| Section: | P.sect. Quinquefoliae |
| Subsection: | P.subsect. Strobus |
| Species: | P. strobiformis |
| Binomial name | |
| Pinus strobiformis | |
 | |
| Natural range (green), with the closely relatedPinus stylesii (orange), andPinus reflexa (blue) | |
| Synonyms | |
Pinus ayacahuite var.strobiformis(Engelm.) Lemmon | |
Pinus strobiformis, also known asChihuahua white pine, is a medium-sizedwhite pine treeendemic to westernMexico in theSierra Madre Occidental mountain range. It is typically a high-elevation pine growing mixed with otherconifers inmontane forest. It was formerly considered conspecific withPinus reflexa (southwestern white pine) of the southwestern United States andPinus stylesii of northeastern Mexico, but is now treated as distinct from these.[2][3][4]
Pinus strobiformis, a member of thewhite pine group,Pinus subgenusStrobus, is a straight, slender tree growing to 30 metres (98 ft) (rarely 40 metres (130 ft)) tall and 1 metre (3 ft 3 in) in diameter. Thebark is smooth and silvery-grey on young trees, aging to furrowed and red-brown or dark grey-brown. The branches are spreading and ascending. The twigs are slender, pale red-brown, aging to smooth grey or grey-brown. The buds are ellipsoid, red-brown, and resinous. Theleaves (needles) are five per bundle (fascicle), spreading, 8–14 cm long, 0.6-1.0 mm in diameter, straight, slightly twisted, pliant, dark green to blue-green, and persist 3–5 years. The upper surfaces (adaxial, facing the centre of the fascicle) is conspicuously whitened by narrowstomatal lines. The lower surfaces (abaxial, the outer face away from the centre of the leaf fascicle) are without evident stomatal lines. The margins are sharp, razorlike and finely serrulate, apex narrowly acute to short-subulate. Each fascicle has adeciduoussheath 1.5-2.0 cm long which is shed early.
The cones are very large, 16–50 cm long and 9–11 cm broad, and have scales with a very characteristic prolonged and often recurved or S-shaped apex. The seeds are large, and with a very short wing; they are dispersed mainly bybirds, particularly theMexican jay.
It is native to Mexico in theSierra Madre Occidental mountains, from a short distance south of theUS–Mexico border south throughChihuahua andDurango toJalisco.[2] The pine rarely appears in pure strands, but grows along with other native conifers, such asDurango pinePinus durangensis,Arizona pinePinus arizonica,American aspenPopulus tremuloides,Durango firAbies durangensis,Douglas-firPseudotsuga menziesii, and the Mexicansubspecies ofEngelmann's sprucePicea engelmannii subsp.mexicana. It is a drought tolerant tree but greater populations grow on moist and cool places living in association with other pines.
