A stand of whitebark pines
The Whitebark pine (Pinus albicaulis; Family Pinaceae) is a species of pine tree that occurs in the mountains of the Western United States and Canada, specifically the subalpine areas of the Sierra Nevada, the Cascade Range, the Coast Range, and the Rocky Mountains. The Whitebark is typically the highest-elevation pine tree of these mountains, marking the timberline. Thus, Whitebark are often found as krummholz: shrubs growing close to the ground.
The Whitebark pine can be distinguished from the Lodgepole pine because it has five needles per bundle growing out of a stem, instead of two for the Lodgepole and three for the Ponderosa pine and the Jeffrey pine.
The Whitebark pine is an important source of food for several species, including Red squirrels and Clark's Nutcrackers. American black bears often raid squirrel caches for the Whitebark pine nuts. Squirrels, Northern flickers, and Mountain bluebirds can nest within the Whitebark.
Unfortunately, the Whitebark pine in Washington, Idaho, Montana, British Columbia, and Alberta are afflicted with White pine blister rust, a fungus that was introduced from Europe. Whitebark pine mortality in some areas are reaching 60%. The blister rust has also decimated the commercially valuable Western white pine in these areas. However, there is no known way of controlling the blister rust.