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Pinus aristata

Description
Pinus aristata is a medium-size tree, commonly reaching 15 m in height and occasionally as much as 20 m in their natural habitat. In favorable conditions they are straight and upright trees, but they become increasingly stunted, short, and twisted the closer they grow to timberline. The crown of the tree is flattened, irregular, or round in shape when fully mature. The trunk can be very substantial, commonly 75 cm and up to 1 m in diameter, and tapers very noticeably towards the top. The bark is fairly smooth and white-gray on young trees, but becomes dark and cracked with a scaly texture on old trees. The color of older bark ranges from red-brown to gray.

On older trees the branches are crooked and twisting and may be partially dead. Twigs begin as red-brown, but become gray with age. Twigs and very young branches are covered in needles that last for 10 to 17 years, giving them a shaggy bottle brush appearance. The needle like leaves are bundles of five and are 2–4 centimeters long, but usually longer than 3 cm. The fascicle, the base that holds the needles together, breaks down more quickly in Pinus aristata than in Pinus longaeva, giving a more even appearance to its branches. The resin canals in the needles are closer to the surface and not as sturdy, explaining the noticeable white flecks of resin. The botanist Dana K. Bailey described the needles covered in resin as appearing "dandruffy". Between the white specks the needles are dark green in color. The buds are egg shaped with a long tapering point, about 1 cm in size.

The pollen cone is approximately 1 cm in length and may be blueish to red colored. Seed cones are dark purple when immature and turn brown as they ripen. At full size they are 6–11 centimeters in length. A seed cone takes two years to fully ripen. Each scale of the cone is tipped with a thin, brittle pickle 4–10 millimeters long. They fall from the tree soon after releasing their seeds. Pinus aristata has seeds that are gray-brown to nearly black in color and 5–6 mm long.

Notable trees
The oldest tree in Colorado is a Rocky Mountain bristlecone that was dated by F. Craig Brunstein and David Yamaguchi to 442 BCE.

Taxonomy
Pinus aristata was scientifically described in 1862 by George Engelmann with its present scientific name. The botanical samples used to describe and name the species were collected in 1861 by Charles Christopher Parry, however the earliest known scientific collection was by Frederick Creuzefeldt in 1853. In 1878 Englemann worked on a reclassification of the taxon as a variety of Pinus balfouriana and in 1880 as a subspecies. It is listed as an accepted species with no subspecies by Plants of the World Online, World Flora Online, and World Plants. Prior to work by Dana K. Bailey published in 1971, Pinus longaeva trees growing in California, Nevada, and Utah were not identified as a separate species or subspecies.

Names
The species name aristata means "bristle" in botanical Latin, a reference to the long points on the ends of the scales of its cones. As the first bristlecone identified, Pinus aristata is still occasionally referred to simply as bristlecone pine, however Pinus longaeva is also sometimes called bristlecone pine in English. To distinguish it from its relative the name Rocky Mountain bristlecone pine is frequently used or the similar Colorado bristlecone pine. The common name hickory pine is used, most often in Colorado, due to the hardness and density of the wood being like that of a hickory. It is additionally known as foxtail pine and wind timber, but the former name is more often applied to Pinus balfouriana.

Range and habitat
The Rocky Mountain bristle cone reaches its northern limit at 40 degrees north latitude.

Rocky Mountain bristle cone will grow in krummholz habitat at the edge of the arctic tundra, where it has the typical dwarfed and gnarled growth of these "crooked woods".

Uses
Prior to its protection it was used for fuel and as support timbers in mines.

Cultivation
In cultivation Rocky Mountain bristlecone is small to medium in size, 8 - 20 ft high and 10 - 15 ft wide.