The dwarf or white-bark pine is the species that forms the timber-line, where it is so completely dwarfed that one may walk over the top of a bed of it as over snow-pressed chaparral. John Muir
This is a slow-growing and long-lived pine found in the mountains of southwest Canada and the western U.S. It is found at the elevational extent of forest at timberline. Its distribution is split into two major regions, the BC Coast Range/Cascades/Sierra and the Rocky Mountains from Wyoming to Alberta. It is absent in very wet pockets of these ranges and is restricted to the northeastern rain shadow areas of the Olympic Mountains, for instance.
Pinus (Greek – pine tree) and albicaulis (white stem). These trees first appear in Meriwether Lewis’s journal as they are crossing Lemhi Pass, but only in a fleeting reference to the feeding habit of Clark’s nutcrackers – birds that eat the seeds and named after the other leader of the expedition.
On favorable sites near the treeline it can grow into a single-trunk tree up to 65 ft. tall and have a life span of about 500 years. Older individuals on cold, dry sites can live up to 1,000 years. The largest one recorded is from Idaho’s Sawtooth Mountains and had a trunk over 8 ft. wide and was 69 ft. tall. John Muir counted 255 annual rings on a 3 ft. high specimen that was only 3.5 inches in diameter! Wow!
Particularly above timberline these trees are known to grow with multi-stems and clumps arising from Clark’s nutcracker caches. The bark is smooth and chalky white on young stems and forms brown, scaly plates as the tree ages. Between 1860 to 1940, billions of board feet of whitebark pine were cut to fuel the Montana mining industry; the wood was used in smelters and to heat miner‘s homes; now less than 1,000 acres in the United States are harvested each year, typically within a timber sale for lodgepole pine.
This tree grows in areas that are cold, windy, and snowy in mountains with a moist climate regime – common on exposed dry slopes. It is found where precipitation ranges from 24 to 72 inches a year. The Cascade Crest is a high precipitation area within its range where it often is found with subalpine fir (Abies lasiocarpa) and mountain hemlock (Tsuga merttensiana). It can withstand deep snow (180 – 500 inches) and can grow in a stunted, krummholz (shrub-like) form on windswept ridges.
Whitebark pine is monoecious (Greek – one house), meaning that an individual plant produces both male and female flowers. The female strobili and cones develop near the tip of upper branches and the male pollen strobili develop throughout the crown of the current year’s growth. Pollen is produced in the first half of July with seeds ripening in the cones by early September. This tree can produce large crops of seeds at irregular intervals. The large, dense seeds are high in fat and are harvested by a number of mammals and birds. Clark’s nutcrackers and red squirrels are particularly adept at feeding on pine nuts. Nutcrackers can carry as many as 50 whitebark pine seeds in their throat pouch and will cache the seeds for later use. In one study these birds cached an estimated 13,600 seeds per acre. The birds don’t recover all their seeds and thus aid in distribution of the plant. Grizzly and black bears feed on the seeds and often will raid squirrel caches that contain pine nuts. It also was an important food for Native Americans.
The cones are green while growing, and are usually found over all the tree, forming quite a marked feature as seen against the bluish-gray foliage. They are quite small, only about two inches in length, and give no promise of edible nuts; but when we come to open them, we find that about half the entire bulk of the cone is made up of sweet, nutritious seeds, the kernels of which are nearly as large as those of hazel-nuts.This is undoubtedly the most important food-tree on the Sierra, and furnishes the Mono, Carson, and Walker River Indians with more and better nuts than all the other species taken together. It is the Indians’ own tree, and many a white man have they killed for cutting it down. John Muir, 1894.
Whitebark pine can be affected by the mountain pine beetle that inhabits the inner bark layer of older trees. Blister rust, a fungus introduced from Europe to the western U.S. in 1910 is a growing problem affecting whitebark pine populations. Recent work in the Rocky Mountains suggests the tree is functionally extinct in more than a third of its former range. Given that it is listed as a critical food source for grizzly bears and other animals there is a growing concern and an increase in research on this pine. Only an estimated 28% of the whitebark pine population displays a resistance to the blister rust. A study conducted in the western Cascades in the mid-2000’s showed that whitebark pine declined by 41% — pine death in the North Cascades National Park doubled from 2006 to 2011 and 80% of the trees in Mount Rainier National Park are infected with blister rust. This is not very reassuring and there is considerable speculation about the effect of warmer winters and reduced snow pack associated with climate change.
I’ve seen this tree out and about in the Cascades from up to 8,000 ft. on Mt. Stuart and as low as about 5,000 ft. in the Teanaway Range, east of the crest. These photos are from the drier side of Mt. Rainier earlier this year just before the snow closed access from Sunrise entrance to the park and on the way to the Fremont Lookout, if you’ve ever been out that way. It is pretty typical habitat – cold and snowy most of the year, dry and rocky with a south exposure in the summer. Because whitebark pine is found so high up, you’re usually in a pretty nice spot when you bump into it.