Bristlecone pines grow in scattered sub-alpine groves at high altitude in arid regions of the Western United States. Bristlecones are among the longest-lived life forms on Earth. The oldest (Pinus longaeva) is more than 5,000 years old, making it the oldest known individual of any species on the planet.

Bristlecone pines grow in isolated groves just below the tree line, between 5,600 and 11,200 ft (1,700 and 3,400 m) elevation on dolomitic soils. The trees grow in soils that are usually derived from dolomite and sometimes limestone, and occasionally sandstone or quartzite soils. Dolomitic soils are alkaline, high in calcium and magnesium, and low in phosphorus. Those factors tend to exclude other plant species, allowing bristlecones to thrive. Because of cold temperatures, dry soils, high winds, and short growing seasons, the trees grow very slowly. Even the tree’s needles, which grow in bunches of five, can remain on the tree for forty years, which gives the tree’s terminal branches the unique appearance of a long bottle brush.

The bristlecone pine’s root system is mostly composed of highly branched, shallow roots, while a few large, branching roots provide structural support. The bristlecone pine is extremely drought tolerant due to its branched shallow root system, its waxy needles, and thick needle cuticles that aid in water retention.

The wood is very dense and resinous, and thus resistant to invasion by insects, fungi, and other potential pests. The tree’s longevity is due in part to the wood’s extreme durability. While other species of trees that grow nearby suffer rot, bare bristlecone pines can endure, even after death, often still standing on their roots, for many centuries. Rather than rot, exposed wood, on living and dead trees, erodes like stone due to wind, rain, and freezing, which creates unusual forms and shapes.