Description. Great Basin bristlecone pine is an evergreen coniferous species of tree that grows to mature heights of 65 feet (16 m) with a trunk up to 80 inches (200 cm) in diameter, measured at breast height; and rounded or irregular crown, sometimes forming krummholz at the alpine timberline.
Bark is colored red-brown, fissured with thick, scaly, irregular, blocky ridges.
Branches are contorted and pendent; twigs are puberulent, pale red-brown in color, aging gray to yellow-gray. Young branches resemble long bottle-brushes because of persistent leaves, closely spaced needle whorls, and uniform needle insertion angles.
Foliar buds are ovoid-acuminate shaped, resinous, colored pale red-brown and measure circa 0.4 inch (1 cm) long.
Leaves (needles) are borne mostly 5 per fascicle, upcurved, persisting 10 to 43 years (among the longest persistence times known). Each needles measures 0.6 to 1.4 inches (15 - 35 mm) long by 0.032 to 0.048 inch (0.8-1.2 mm) thick, colored deep yellow-green, with few resin splotches, but often scurfy with pale scales. Abaxial surfaces lack median grooves but has 2 sub-epidermal bands of resin. Adaxial surfaces are conspicuously whitened with stomata. Margins are entire or remotely and finely serrulate distally, with bluntly acute to short-acuminate apex. Foliar sheaths measure circa 0.4 inch (1 cm), forming a rosette soon after needle push, then shed early.
Pollen cones are cylindro-ellipsoid shaped, colored purple-red, and measure 0.28 to 0.4 inch (7 - 10 mm) long.
Seed cones mature 2 years after pollination, shedding seeds and falling soon thereafter. Each cone is spreading, symmetric to lance-cylindric shaped with a rounded base before opening; lance-cylindric to narrowly ovoid when open, purple colored, aging red-brown, nearly sessile, and measuring 2.4 to 3.8 inches (6 - 9.5 cm) long. Apophyses are thickened, sharply keeled; umbo is central to the seed scale, raised on a low buttress, truncate to umbilicate, abruptly narrowed to slender but stiff, including a variable prickle measuring 0.04 to 0.24 inch (1 - 6 mm). Cones exude pale resin.
Seeds are ellipsoid-obovoid shaped with a body colored pale brown, mottled with dark red, measuring 0.2 to 0.32 inch (5 - 8 mm) long with a 0.4 to 0.48 inch (10 - 12 mm) wing.
Distribution. This species is native to USA — California, Nevada & Utah. Growing at subalpine and at the upper (rarely, lower) treeline; typically at elevations of 5,600 to 11,000 feet (1,700 - 3400 m) above sea level.
In many sites it shows a distinct preference for carbonate (limestone, dolomite or marble) substrates. In California's White mountains, for example, the limit of the bristlecone grove coincides with a dolomite/sandstone contact. Bristlecones grow at remarkably high elevations. For example, on Wheeler Peak, Nevada, there are four timberlines - a lower timberline set by the heat and aridity of the valley floor desert, and above that, a timberline set by cold that defines the upper limits of piñon pine (Pinus monophylla) and juniper (Juniperus osteosperma). Still higher, there is a lower timberline of bristlecone pine defined by its tolerance of heat and drought, and above that is a final timberline beyond which winter's cold prevents even bristlecone from growing.
Hardy to USDA Zone 4 — cold hardiness limit between -30° and -20°F (-34.3° and -28.9°C).