Pinus flexilis

Limber pine or Rocky Mountain white pine is a member of the pine or Pinaceae family and is native to the mountains of the western United States, Mexico, and Canada. It is a small, slow-growing tree often with a crooked trunk and irregular branches, reaching less than 10 m tall at high elevations.

• Needles are 5 per fascicle, 7–10 cm long, rigid, with a deciduous sheath, needles smooth when rubbed gently in both directions, unlike a similar species, western white pine (P. monticola) which are finely serrated (feel rough when rubbed gently from tip to base).
• Branches are in yearly whorls.
• Species is monoecious; male pollen cones are small and reddish brown; young female cones are bright reddish-purple, maturing in 2 years.
• Mature seed cones are 6–12 cm long, on a short stock, scales unarmed, being non-serotenous (they open when mature), falling off the tree; scales are thick at the tip, spoon-shaped, unarmed. A similar species, whitebark pine (P. albicaulis), is distinguished by having smaller (4–7 cm long), serotenous (do not open when mature) cones which remain on the tree after maturing.
• Twigs are stout, very flexible (can be tied into knots), silvery-white to gray, drooping with age, tips often turning up; bark is initially thin, smooth, gray-white, later turning brown with deep fissures and square plates.
• Limber pine and western white pine are both susceptible to white pine blister rust.
• A popular cultivar of limber pine is 'Vanderwolf's Pyramid' (P. flexilis 'Vanderwolf's Pyramid').