Pinus hartwegii


Pinus hartwegii, Hartweg's pine, is a pine native to the mountains of Mexico and Central America east to Honduras. It is named after Karl Theodor Hartweg, who discovered it in 1838.

Distribution

Pinus hartwegii is a very high altitude species, growing at altitudes of. It forms the alpine tree line on most of Mexico's higher mountains. It grows on both the Sierra Madre Occidental and Sierra Madre Oriental from Chihuahua State and Nuevo León to the highest peaks in the mountain ranges on the El Salvador—Honduras border. 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 altitudes. Even at the alpine tree line, this tree is not damaged by the cold and wind-blown ice present at that altitude. Consequently, Pinus hartwegii has been studied as an evolutionarily unique member on tree line ecophysiology.
, Mexico

Description

Pinus hartwegii is an evergreen tree reaching in height, with a broad, rounded crown. The bark is thick, dark grey-brown, and scaly or fissured. The leaves are needle-like, dark green, five per fascicle, 10–20 cm long and 1.2-1.5 mm thick, the persistent fascicle sheath 1.5–2 cm long.
The cones are ovoid, 6–13 cm long, black or very dark purple, opening when mature in spring to 5–7 cm broad. The seeds 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 , differing from it in the shorter leaves, black and smaller cones; it replaces Montezuma pine at high altitudes, and often hybridises with it where they meet at middle altitudes.