The limber pine, Pinus flexilis, is a pine tree species in the Pinaceae family that grows in the mountains of the Western United States, Mexico, and Canada. Rocky Mountain white pine is another name for it. Fascicules (bundles) comprising five leaves (needles) with a deciduous sheath. This sets it apart from Lodgepole Pines, which have two needles per fascicle, and Bristlecone Pines, which have five needles per fascicle but a semi-persistent sheath.