Pinus contorta subsp. contorta

Common names

Shore pine (Kral 1993).

Taxonomic notes

There is one variety, P. contorta subsp. contorta var. bolanderi (Parlatore) Koehne 1893 (syn: Pinus bolanderi Parlatore; P. contorta subsp. bolanderi (Parlatore) Critchfield).

Description

Trees to 10 m tall and 50 cm dbh, straight or, in exposed sites, contorted and bent (ordinarily with a bowed base and then straight above 1 m), or reduced to shrub form by wind shear and salt spray in extreme exposure; mature crown irregularly rounded or flat. Bark thicker than in the other subspecies, irregularly furrowed, cross-checked into small, square or rectangular, orange-brown to purple-brown scaly plates. Branches spreading, often contorted. Leaves (2-)3-6(-7) cm × 1.2-1.8 mm, dark green, apex acute to broadly acute or blunt. Seed cones maturing and shedding seeds in 18 months, persistent or variously serotinous, 3-6.5 (-7.5) cm long, orange-brown, usually moderately to often strongly asymmetric and/or recurved, reflexed down branch, often in whorls, proximal outer apophyses weakly to strongly domed (Kral 1993, Frankis, M.P. pers. obs. 1999.02.28).

Var. bolanderi differs mainly in leaf anatomy, usually having no resin canals or rarely one (c.f. usually two in the type), and the cones average slightly heavier with thicker scales (Critchfield 1957); it also differs in resin composition and genetic makeup (Wheeler and Guries 1982, von Rudloff and Lapp 1987). It is more commonly a shrub, but this is an environmental effect due to poor growing conditions on highly podsolised white sands (Aitken and Libby 1994); when cultivated in Britain, its growth form is closely similar to the type (Frankis 1999).

Distribution and Ecology

USA: Alaska, Washington, Oregon, NW California; Canada: British Columbia. Found in maritime fog forests, bogs, and dry foothills at 0-600 m elevation (Kral 1993).

This is the typical subspecies, and the one responsible for the species' epithet contorta. When David Douglas discovered this tree in 1826, he found it growing on exposed rocky sites near the mouth of the Columbia River. On inadequate soils and exposed to salt spray, the trees grew in short, gnarly, contorted shapes. That particular growth form has since been found to be attributable to formation of the growth substance coumarin in trees with foliage damaged by exposure to salt air or windblown ice crystals, explaining the similarity of appearance between trees growing at the alpine timberline and trees growing on the seashore (Löve et al. 1970). On more sheltered sites, subsp. contorta grows as a tall erect tree, very similar in appearance to subsp. latifolia. Refer to the Distribution and Ecology discussion of subsp. latifolia for remarks on tolerance to poor soils and adaptations to fire. In subsp. contorta, adaptation to poor soils in the form of bogs is particularly widespread from Washington to Alaska; a photo of this habitat it shown at right. Adaptation to rocky sites is largely restricted to maritime settings, i.e. within a few kilometers of salt water. In contrast, a "lodgepole" growth form with adaptation to stand-destroying fire is the normative condition in subsp. latifolia, but is uncommon in subsp. contorta.

Var. bolanderi is confined to the highly podsolised Mendocino white sands in California; see Aitken and Libby (1994) for description of the vile growing conditions it has to tolerate, including minimal rooting depth above an impermeable hardpan, anaerobic winter flooding, severe summer drought and a soil pH of 2.9 (about as acid as vinegar!).

Similar species: see the Pinus contorta page.

Remarkable Specimens

Currently, the largest is a specimen in Snohomish, Washington measured in 2018 at 123 cm dbh and 37.8 m tall (American Forests 2021). The largest recorded specimen in its native range was height 31 m, dbh 112 cm, crown spread 11 m, found in Bryant, Washington in the 1990's, but it was killed by bark beetles in about 2017-2018 (American Forests 1996, R. Brightman email 2018.08.17). Some comparably large trees exist in cultivation in Britain: 34 m tall at Bodnant, N Wales, and 114 cm diameter at Errol House, Scotland (Mitchell et al. 1990); these are planted on better quality soils than those accessible to the species in the wild where it is usually excluded on good sites by competition with associated conifers such as Picea sitchensis or Pseudotsuga menziesii subsp. menziesii.

Var. bolanderi is the smallest of all pines and among the smallest of all conifers, with sexually mature individuals as short as 20 cm recorded.

There are few age data. I sampled a tree in a Washington bog that turned out to be a bit over 100 years old.

Ethnobotany

USDA hardiness zone 7. This is one of the most important afforestation species in Britain, where its main uses are as a nurse for Picea sitchensis on poor and highly exposed sites, and for planting on coal-mining spoil heaps where it is one of the few trees that will grow successfully. It is often cut for Christmas trees, though it is not a good species for that purpose.

Observations

The species is widely distributed and common within its range. I have seen it, for instance, at Jones Island, Moran, Larrabee, Damon Point and Pacific Pines State Parks in Washington, and at Patrick's Point State Park in California. One of its most interesting occurrences is at Deer Park near the northeast corner of Olympic National Park in Washington. This site receives relatively low rainfall and has a well-defined summer drought, conditions that predispose the location to frequent fire. At this location the trees have a growth form and landscape distribution precisely like that of subspecies latifolia where it grows in dense, fire-prone stands. Nearby, the trees can also be found growing as krummholz at the alpine timberline.

Remarks

Citations

Aitken, S. N. and W. J. Libby. 1994. Evolution of the pygmy-forest edaphic subspecies of Pinus contorta across an ecological staircase. Evolution 48: 1009-1019.

American Forests 1996. The 1996-1997 National Register of Big Trees. Washington, DC: American Forests.

Critchfield, W. B. 1957. Geographic variation in Pinus contorta. Maria Moors Cabot Foundation (Harvard) Publ. 3.

Frankis, M. P. 1999. E-mail describing personal observations of trees at Kew Gardens.

von Rudloff, E. and M. S. Lapp. 1987. Chemosystematic studies in the genus Pinus. VI. General survey of the leaf oil terpene composition of lodgepole pine. Canadian Journal of Forest Research 17: 1013-1025.

Wheeler, N. C. and R. P. Guries. 1982. Population structure, genic diversity, and morphological variation in Pinus contorta Dougl. Canadian Journal of Forest Research 12: 595-606.

M.P. Frankis co-edited this page, 1999.02.

See also