Pinus flexilis aka Limber Pine

Pinus flexilis, or limber pine, is an evergreen conifer. It belongs to the pine family, Pinaceae. Its native range spans western Canada and the western United States. It grows through the Rocky Mountains, south to New Mexico. Wild trees grow on dry slopes and near the tree line. Harsh winds can shape them into small, twisted shrubs.

Garden trees reach 25–60 feet [7.6–18.3 metres] in height. Several sources give a narrower range of 30–50 feet [9.1–15.2 metres]. Spread can reach 35–40 feet [10.7–12.2 metres]. Young trees form a dense pyramid. Older trees develop a broad, rounded or flat crown. Growth ranges from slow to moderate. Young bark looks smooth and pale gray. With age, it darkens and splits into rough, scaly plates. Tough, flexible shoots give the tree its common name.

The green to blue-green needles grow in groups of five. Fine white lines mark their surfaces. Needles can stay on the branches for five or six years. This keeps much of each branch clothed in green. Male and female cones grow on the same tree. Chicago Botanic Garden lists March to April for bloom. Woody seed cones measure 0.25–0.67 feet [0.08–0.20 metres] long. Their thick scales open as the cones turn brown. Large seeds usually lack wings. The cones fall whole rather than breaking apart.

Full sun gives the best growth, though trees accept partial shade. Moist soil with good drainage suits them best. They also tolerate dry ground and a range of conditions. Sources place them in USDA zones 4–7. Missouri Botanical Garden advises against planting south of zone 7. A deep taproot makes older trees hard to move. Limber pine serves as a specimen, screen or shade tree. Its year-round needles add winter interest. Birds and small mammals eat the seeds. It also hosts imperial moth larvae and resists deer browsing.

Care needs are low, but serious disease can occur. White pine blister rust attacks the bark and can kill trees. Currants and gooseberries serve as alternate hosts for this disease. Rots and blights can also occur. Pests include aphids, weevils, spider mites and scale. PFAF lists seeds and inner bark as edible parts. People can eat the seeds raw or cooked. Ground seeds can thicken soup or go into baked goods. PFAF warns that pine wood, dust and resin may irritate sensitive skin. That warning covers several pine species, not this tree alone.