''Pinus hartwegii'' ( syn. ''P. rudis'', ''P. donnell-smithii''), Hartweg's pine, the Mexican mountain pine, or pino de las alturas, is a

pine A pine is any conifer tree or shrub in the genus ''Pinus'' () of the family Pinaceae. ''Pinus'' is the sole genus in the subfamily Pinoideae. ''World Flora Online'' accepts 134 species-rank taxa (119 species and 15 nothospecies) of pines as cu ...

native to the

mountain A mountain is an elevated portion of the Earth's crust, generally with steep sides that show significant exposed bedrock. Although definitions vary, a mountain may differ from a plateau in having a limited summit area, and is usually higher t ...

s of

Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...

and

Central America Central America is a subregion of North America. Its political boundaries are defined as bordering Mexico to the north, Colombia to the southeast, the Caribbean to the east, and the Pacific Ocean to the southwest. Central America is usually ...

east to

Honduras Honduras, officially the Republic of Honduras, is a country in Central America. It is bordered to the west by Guatemala, to the southwest by El Salvador, to the southeast by Nicaragua, to the south by the Pacific Ocean at the Gulf of Fonseca, ...

. It is named after

Karl Theodor Hartweg Karl Theodor Hartweg (18 June 1812 – 3 February 1871) was a German botanist. He collected numerous new species of plants in Colombia, Ecuador, Guatemala, Mexico and California in the United States, collecting for the London Horticultural Society ...

, who described it in 1838.

Distribution

''Pinus hartwegii'' is a very high elevation species, growing at elevations of . It forms the alpine tree line on most of Mexico's higher mountains. It grows on both the

Sierra Madre Occidental The Sierra Madre Occidental is a major mountain range system of the North American Cordillera, that runs northwest–southeast through northwestern and western Mexico, and along the Gulf of California. The Sierra Madre is part of the American C ...

and

Sierra Madre Oriental The Sierra Madre Oriental () is a mountain range in northeastern Mexico. The Sierra Madre Oriental is part of the American Cordillera, a chain of mountain ranges (cordillera) that consists of an almost continuous sequence of mountain ranges that ...

(mountain ranges) (29° North latitude) from Chihuahua State and

Nuevo León Nuevo León, officially the Free and Sovereign State of Nuevo León, is a Administrative divisions of Mexico, state in northeastern Mexico. The state borders the Mexican states of Tamaulipas, Coahuila, Zacatecas, and San Luis Potosí, San Luis ...

(26°) to the highest peaks in the mountain ranges on the

El Salvador El Salvador, officially the Republic of El Salvador, is a country in Central America. It is bordered on the northeast by Honduras, on the northwest by Guatemala, and on the south by the Pacific Ocean. El Salvador's capital and largest city is S ...

—

border (15° North latitude). In the Sierra Madre Occidental this pine grows with very dry winters and a very heavy rainy season in summer, with constant frosts from October to March. This pine does not acquire the dwarfed and contorted shape shared by many species at high elevation. Even at the alpine

tree line The tree line is the edge of a habitat at which trees are capable of growing and beyond which they are not. It is found at high elevations and high latitudes. Beyond the tree line, trees cannot tolerate the environmental conditions (usually low ...

, this tree is not damaged by the cold and wind-blown ice present at that elevation. Consequently, ''Pinus hartwegii'' has been studied as an evolutionarily unique member on tree line

ecophysiology Ecophysiology (from Greek , ''oikos'', "house(hold)"; , ''physis'', "nature, origin"; and , '' -logia''), environmental physiology or physiological ecology is a biological discipline that studies the response of an organism's physiology to envir ...

Description

''Pinus hartwegii'' is an

evergreen In botany, an evergreen is a plant which has Leaf, foliage that remains green and functional throughout the year. This contrasts with deciduous plants, which lose their foliage completely during the winter or dry season. Consisting of many diffe ...

tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, e.g., including only woody plants with secondary growth, only ...

reaching in height, with a broad, rounded crown. The

bark Bark may refer to: Common meanings * Bark (botany), an outer layer of a woody plant such as a tree or stick * Bark (sound), a vocalization of some animals (which is commonly the dog) Arts and entertainment * ''Bark'' (Jefferson Airplane album), ...

is thick, dark grey-brown, and scaly or fissured. The

leaves A leaf (: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, ...

are needle-like, dark green, five (occasionally four) per fascicle, 10–20 cm long and 1.2-1.5 mm thick, the persistent fascicle sheath 1.5–2 cm long. The

cones In geometry, a cone is a three-dimensional figure that tapers smoothly from a flat base (typically a circle) to a point not contained in the base, called the ''apex'' or '' vertex''. A cone is formed by a set of line segments, half-lines, ...

are ovoid, 6–13 cm long, black or very dark purple, opening when mature in spring to 5–7 cm broad. The

seed In botany, a seed is a plant structure containing an embryo and stored nutrients in a protective coat called a ''testa''. More generally, the term "seed" means anything that can be Sowing, sown, which may include seed and husk or tuber. Seeds ...

s are winged, 5–6 mm long with a 1.5-2.5 cm wing. Pollination is in late spring, with the cones maturing 20–22 months after. It is closely related to ''Pinus montezumae'' (Montezuma pine), differing from it in the shorter leaves, black (not brown) and smaller cones; it replaces Montezuma pine at high elevations, and often hybridises with it where they meet at middle elevations.

References

External links

{{Taxonbar, from=Q136695 hartwegii Trees of Guatemala Trees of El Salvador Trees of Honduras Trees of Northern America Flora of Northeastern Mexico Flora of the Sierra Madre Occidental Flora of the Sierra Madre Oriental Flora of the Trans-Mexican Volcanic Belt Least concern flora of North America