Russell T. Graham
Western white pine (Pinus monticola), also called mountain white pine, Idaho white pine, or silver pine, is an important timber tree. Its lightweight, nonresinous, straight-grained wood exhibits dimensional stability that makes it particularly valuable for sash, frames, and doors, interior paneling, building construction, match wood, and toothpicks. Western white pine grows rapidly to a large size; one of the largest standing trees measures 200 cm (78.6 in) in d.b.h. and 72.8 m (239 ft) tall in the mountains near Medford, OR.
Global Range: Western white pine occurs only in western North America from British Columbia to California, eastwards to Utah and Montana.
boundary of its range is at Quesnel Lake, British Columbia, latitude 52
deg. 30 min. N., and the southern boundary is at Tulare County,
California, latitude 35 deg. 51 min. N. The western boundary is marked
by the Pacific Coast, and the eastern boundary is at Glacier National
Park, Montana. Western white pine reaches its greatest size and best
stand and commercial development in northern Idaho and adjacent parts of
Montana, Washington, and British Columbia .
Regional Distribution in the Western United States
This species can be found in the following regions of the western United States (according to the Bureau of Land Management classification of Physiographic Regions of the western United States):
1 Northern Pacific Border
2 Cascade Mountains
4 Sierra Mountains
8 Northern Rocky Mountains
Occurrence in North America
In the interior, western white pine grows from latitude 52° 30' N. near Quesnel Lake, BC, southward through the Selkirk Mountains of eastern Washington and northern Idaho, and into the Bitterroot Mountains in western Montana. Its southernmost interior limit is in the Blue Mountains of northeastern Oregon (latitude 44° 14' N.). Isolated populations are found as far east as Glacier National Park, MT. It attains its greatest size and reaches its best stand and commercial development in the Inland Empire, which includes northern Idaho and adjacent sections of Montana, Washington, and British Columbia (28).
- The native range of western white pine.
Western white pine is a native, evergreen, long-lived (400+ years),
monoecious tree [9,11,16,44]. It can reach 200 feet (60 m) in height
and 8 feet (2.4 m) in d.b.h. The needles, 2 to 4 inches (5-10 cm) long,
are in bundles of five. The bark on young trees is smooth and grayish
green but on mature trees becomes grayish brown, scaley, and separated
into rectangular plates . The crown is narrow and composed of
regularly spaced branches . In dense stands western white pine
self-prunes well, leaving a long, clean bole .
The root system consists of a taproot and lateral roots which can spread
up to 26 feet (8 m). Most (75 percent) of the lateral roots are in the
upper 24 inches (60 cm) of soil .
The male strobili are yellow, and the female strobili are reddish
purple. Mature female strobili are 5 to 15 inches (12-38 cm) in length
The early growth of western white pine is not rapid, but it is the
fastest growing sapling and pole-sized tree in the Northern Rockies
Comments: Western white pine occurs on a wide variety of sites from peat bogs to dry sandy soils and rocky ground, however it grows best in moist valleys or on slopes at near sea level to mid-elevations in mountains.
Habitat and Ecology
summers and a predominance of winter precipitation . The most
extensive and best stands of western white pine are found in the river
bottoms and less steep lower slopes of the Priest, Coeur d'Alene, St.
Joe, and Clearwater River basins . In British Columbia, western
white pine is a minor species on moderately dry to wet, nutrient-medium
to nutrient-rich sites in the maritime and submaritime climates .
Here, western white pine requires sites fairly rich in calcium and
magnesium . However, in the coastal Northwest, western white pine
becomes abundant only on poor sites, where it can outcompete Douglas-fir
(Pseudotsuga menziesii) and other conifers. It does well on
unproductive, gravelly soils in the Puget Sound area and reportedly
thrives at the edges of bogs on the Olympic Peninsula .
Soils: Western white pine grows on a wide variety of soils within its
range, the majority of which have been classified as Spodosols .
Along the West Coast, it attains best development on deep, porous soils,
but it is most common on poor, sandy soils. In northern Idaho and other
inland sites, it is found on shallow to deep soils, with the surface
layers composed of loess or loessial-like material. Parent materials
include granite, shist, basalt, and sedimentary rocks. The pH ranges
from 4.5 to 6.8 with a mean of 5.4 .
Elevation and topography: Western white pine is generally a montane
species, but grows at a wide range of elevations [11,72]. Elevational
ranges vary as follows :
Area Feet Meters
British Columbia 0 to 1,480 0 to 450
Vancover Island, BC 0 to 3,940 0 to 1,200
California 6,000 to 10,990 1,830 to 3350
Idaho 1,540 to 5,910 500 to 1,800
Montana 1,540 to 5,910 500 to 1,800
Oregon 6,000 to 7,020 1,830 to 2140
Washington 0 to 6,070 0 to 1,850
Associated species: In Washington, Oregon, and the Inland Empire,
western white pine grows in communities that are rich in other woody and
herbaceous flora, but in the Sierra Nevada associated vegetation is
usually sparse . In addition to those previously listed under
Distribution and Occurrence, overstory associates include Pacific silver
fir (Abies anabilis), noble fir (A. concolor), whitebark pine (Pinus
albicaulis), foxtail pine (P. balfauriana), limber pine (P. flexilis),
sugar pine (P. lambertiana), Jeffrey pine (P. jeffreyi), quaking aspen
(Populus tremuloides), and paper birch (Betula papyrifera) .
Understory associates include Pacific yew (Taxus brevifolia),
huckleberry (Vaccinium spp.), willow (Salix spp.), honeysuckle (Lonicera
spp.), currant, Rocky Mountain maple (Acer glabrum), snowberry
(Symphoricarpus spp.), ocean-spray (Holodiscus discolor), serviceberry
(Amelanchier alnifolia), pachistima (Pachistima myrsinites), sedges
(Carex spp.), pinegrass (Calamagrostis rubescens), false-solomons-seal
(Smilacina), wild ginger (Asarum caudatum), and queencup beadlily .
Key Plant Community Associations
Western white pine is a seral species that is present in a number of
habitat types, associations, and communities throughout its range. In
northern Idaho and eastern Washington, it may dominate early
successional stages of the western hemlock (Tsuga heterophylla)/queencup
beadlily (Clintonia uniflora) and western redcedar (Thuga
plicata)/queencup beadlily habitat types . It is also a major seral
species in the western hemlock/queencup beadlily habitat type in western
Monatana and is a major constituent of the western hemlock zone in the
Puget Sound area of Washington . A western white pine riparian
dominance type has been described for northwestern Montana .
Associated species are those associated with the Aralia phase of the
subalpine fir (Abies lasiocarpa)/queencup beadlily habitat type .
Western white pine is moderately abundant, usually growing in small
groups and often interspersed with other species, in the subalpine
forest zone on the west slope of the Sierra Nevada .
This species is known to occur in the following ecosystem types (as named by the U.S. Forest Service in their Forest and Range Ecosystem [FRES] Type classification):
FRES22 Western white pine
FRES23 Fir - spruce
FRES24 Hemlock - Sitka spruce
FRES26 Lodgepole pine
Habitat: Cover Types
This species is known to occur in association with the following cover types (as classified by the Society of American Foresters):
205 Mountain hemlock
206 Engelmann spruce - subalpine fir
207 Red fir
210 Interior Douglas-fir
212 Western larch
213 Grand fir
215 Western white pine
218 Lodgepole pine
224 Western hemlock
226 Coastal true fir - hemlock
227 Western redcedar - western hemlock
228 Western redcedar
229 Pacific Douglas-fir
230 Douglas-fir - western hemlock
237 Interior ponderosa pine
247 Jeffrey pine
256 California mixed subalpine
Habitat: Plant Associations
This species is known to occur in association with the following plant community types (as classified by Küchler 1964):
K001 Spruce - cedar - hemlock forest
K002 Cedar - hemlock - Douglas-fir forest
K003 Silver fir - Douglas-fir forest
K004 Fir - hemlock forest
K005 Mixed conifer forest
K007 Red fir forest
K012 Douglas-fir forest
K013 Cedar - hemlock - pine forest
K014 Grand fir - Douglas-fir forest
Soils and Topography
Soils of the Inland Empire western white pine region are very diverse. Soil depths range from 25 cm (10 in) to over 230 cm (90 in) and have developed from decomposed granite, schist, quartzite, argillite, sandstone, and shale. Most often, the more rocky soils have developed from basalt, glacial deposits, alluvial deposits, or lacustrine deposits (28). In the Inland Empire, the upper soil layers that support western white pine are composed of loess or loessial-like material. As along the west coast, most of the soils that support western white pine in the Inland Empire are Spodosols.
The pH of soils supporting western white pine in the Inland Empire ranges from 4.5 to 6.8 with a mean near 5.4 (6). The cation exchange capacity of these soils ranges from 20.5 to 28.5 meq/100 g with a mean of 25.1 meq/100 g. Mean concentrations of potassium, calcium, and magnesium are 0.5, 10.5, and 0.8 meq/100 g, respectively. Nitrogen content of soils of the Inland Empire western white pine range varies from 0.14 percent to 0.48 percent with a mean of 0.25 percent.
Western white pine grows at a wide range of elevations. In interior British Columbia, it grows at elevations up to 450 m (1,480 ft), while on Vancouver Island it is normally found at elevations up to 1200 m (3,940 ft) and has been found at elevations over 1500 m (4,920 ft). In western Washington, western white pine is found growing at sea level (near Puget Sound) and up to 910 m (2,980 ft) in elevation in the Cascades. Farther south in the western Cascades, it grows between elevations of 600 and 1850 m (1,970 and 6,070 ft). On the eastern side of the Cascades, it is found growing between elevations of 350 and 1450 m (1,150 and 4,760 ft). In the Olympic Mountains, the species ranges from sea level to an elevation of 550 m (1,800 ft). In the Siskiyou Mountains, western white pine is found at elevations from 1830 to 2140 m (6,000 to 7,020 ft). Farther south in the Sierra Nevada, it usually grows at elevations from 1830 to 2300 m (6,000 to 7,550 ft) with occasional trees at elevations of 3350 m (10,990 ft).
In northern Idaho and contiguous parts of Washington, Montana, and British Columbia, western white pine usually grows between 500 m (1,640 ft) and 1800 m (5,910 ft). Here the topography is usually steep and broken with V-shaped and round-bottomed valleys. Western white pine can grow on a variety of slopes and aspects but is most common along moist creek bottoms, lower benches, and northerly slopes. The most extensive bodies of western white pine are found in the wide river bottoms, less steep lower slopes, and in the more gently rolling country of the Priest, Coeur d'Alene, St. Joe, and Clearwater River basins (28).
In the Sierra Nevada where western white pine grows, the mean annual precipitation varies from 760 to 1500 mm (30 to 59 in). Except for occasional summer thunderstorms, this total falls entirely as snow. The temperature of the area averages between -9° C (15° F) in February to 27° C (80° F) in July and August, with maximum temperature near 37° C (98° F) and a minimum temperature near -32° C (-26° F). In the Sierra Nevada, frost-free days of the western white pine range average between 90 and 180 days, but killing frosts can occur at any time.
The climate of the Inland Empire in the western white pine range is influenced by the Pacific Ocean some 400 km (248 mi) to the west. The summers are dry, the majority of the precipitation occurring during the fall and winter. Precipitation averages between 710 and 1520 mm (28 and 60 in), distributed seasonally as follows: 35 percent, winter; 24 percent, spring; 14 percent, summer; and 27 percent, fall (28). Snowfall averages 262 cm (103 in) but ranges from 122 cm (48 in) to 620 cm (244 in). Annual temperatures in the inland range of western white pine average from 4° to 10° C (40° to 50° F) with extremes of -40° and 42° C (-40° and 107° F). The growing season for western white pine in the Inland Empire is irregular depending on location and year but averages between 60 and 160 days (28).
The boundaries of the western white pine range in the Inland Empire are limited at the lower elevations by deficient moisture and at the upper elevations by cold temperatures. The southern boundary of the type in the Inland Empire is not fixed by insufficient precipitation alone, but by a balance of precipitation and evaporation (28).
Habitat & Distribution
subcortical pycnium of Cronartium ribicola parasitises stem of Pinus monticola
Remarks: season: 3-6
Other: major host/prey
Associated Forest Cover
In the 17 other cover types, western white pine is a common component, along with many other species, including Pacific silver fir (Abies amabilis), white fir (A. concolor), noble fir (A. procera), Port-Orford-cedar (Chamaecyparis lawsoniana), incense-cedar (Libocedrus decurrens), Sitka spruce (Picea sitchensis), whitebark pine (Pinus albicaulis), foxtail pine (P. balfouriana), limber pine (P. flexilis), sugar pine (P. lambertiana), Jeffrey pine (P. jeffreyi), Pacific yew (Taxus brevifolia), Pacific madrone (Arbutus menziesii), bigleaf maple (Acer macrophyllum), red alder (Alnus rubra), quaking aspen (Populus tremuloides), and paper birch (Betula papyrifera). These cover types are as follows:
205 Mountain Hemlock
206 Engelmann Spruce-Subalpine Fir
207 Red Fir
210 Interior Douglas-Fir
212 Western Larch
213 Grand Fir
218 Lodgepole Pine
224 Western Hemlock
226 Coastal True Fir-Hemlock
227 Western Redcedar-Western Hemlock
228 Western Redcedar
229 Pacific Douglas-Fir
230 Douglas-Fir-Western Hemlock
237 Interior Ponderosa Pine
247 Jeffrey Pine
256 California Mixed Subalpine
In northern Idaho and eastern Washington, the most important habitat types in which western white pine grows are Tsuga heterophylla / Clintonia uniflora, Thuja plicata / Clintonia uniflora, and Abies grandis / Clintonia uniflora (6). Western white pine is a major seral species in the Tsuga heterophylla / Clintonia uniflora habitat type in western Montana and is also present in several others (21). Western white pine is present in several vegetative associations, communities, and zones in western Oregon and Washington but is a major constituent only of the Tsuga heterophylla zone in the Puget Sound area of Washington (5,11,14).
Most of the habitat types, associations, and communities in Washington, Oregon, and the Inland Empire where western white pine grows are strikingly rich in other woody and herbaceous flora (5,6,11,14,21). In contrast, in the Sierra Nevada the vegetation associated with western white pine is characteristically sparse. Shrubs associated with western white pine include huckleberry (Vaccinium spp.), willow (Salix spp.), honeysuckle (Lonicera spp.), wintergreen (Gaultheria spp.), azalea (Rhododendron spp.), prickly currant (Ribes lacustre), sticky currant (R. viscosissimum), Rocky Mountain maple (Acer glabrum), Greenes mountain-ash (Sorbus scopulina), princes-pine (Chimaphila umbellata), snowberry (Symphoricarpos albus), whipplea (Whipplea modesta), ocean-spray (Holodiscus discolor), serviceberry (Amelanchier alnifolia), ninebark (Physocarpus malvaceus), rustyleaf menziesia (Menziesia ferruginea), spirea (Spiraea betulifolia), pachistima (Pachistima myrsinites), and twinflower (Linnaea borealis). Graminoids frequently associated with western white pine include sedge (Carex spp.), woodrush (Luzula spp.), Columbia brome (Bromus vulgaris), pine grass (Calamagrostis rubescens), and nodding trisetum (Trisetum cernuum). Forbs found growing with western white pine include false solomons-seal (Smilacina spp.), twistedstalk (Streptopus spp.), coolwort (Tiarella spp.), violet (Viola spp.), wild ginger (Asarum caudatum), queenscup (Clintonia uniflora), western goldthread (Coptis occidentalis), bunchberry (Cornus canadensis), sweetscented bedstraw (Galium triflorum), white trillium (Trillium ovatum), and Brewers lupine (Lupinus breweri).
Diseases and Parasites
Western white pine when dormant is tolerant of cold and along with lodgepole pine is one of the more frost-tolerant northwestern species. Needle desiccation can occur when cold, drying winds cause excessive loss of moisture that cannot be replaced fast enough because of cold or frozen soil or tree trunks. Also, western white pine is more tolerant of heat than most of its more shade-tolerant associates.
The species is sensitive to both sulfur dioxide and fluoride smelter fumes, which cause the foliage to yellow and drop prematurely (15,20). Depending on the site, western white pine is relatively windfirm, but considerable damage can occur from windthrow. Snow often causes breakage in young pole stands.
Western white pine is beset by many serious diseases (15). By far the most prominent disease of western white pine is blister rust. In northern Idaho and contiguous parts of Montana and Washington, a combination of climate, abundant alternate host plants (species of Ribes), and susceptible pines contribute to heavy losses. But, through selection of naturally rust resistant trees for seed sources for natural regeneration and planting of rust resistant nursery stock, damage to western white pine stands from blister rust in the future should be minimal. Other stem diseases, such as dwarf mistletoe, Arceuthobium laricis, and A. tsugense, occur on western white pine; however, they are of little consequence.
In prolonged periods of drought, pole blight, a physiological disorder, can occur in stands of the 40- to 100-year class, causing yellow foliage and dead resinous areas on the trunk. Later the top dies and, in a few years, the tree. The disease does not appear to be caused by a primary pathogen but results from rootlet deterioration in certain soils restricting the uptake of water. The disease, a consequence of a drought from 1916 to 1940 (19), caused serious mortality to western white pine from 1935 to 1960. At present, the disease is not a major cause of mortality in western white pine stands. In conjunction with pole blight studies, root lesions caused by Leptographium spp. were isolated; these could have a role in the decline caused by pole blight.
A needle blight, caused by Lecanosticta spp., often leads to shedding of foliage more than I year old. Another foliage disease that attacks mainly the upper and middle crown is needle cast caused by Lophodermella arcuata. Two other needle cast fungi, Bifusella linearis and Lophodermium nitens, attack isolated trees.
The foremost root disease of western white pine is Armillaria spp., causing fading foliage, growth reduction, root-collar exudation of resin, dead and rotten roots, and black rhizomorphs. Heterobasidion annosum and Phellinus weiri also cause some mortality of individuals and groups. The most important butt-rot fungi are Phellinus pini, Heterobasidion annosum, and Phaeolus schweinitzii. Many other fungi are capable of causing decay in injured or overmature trees, and rot often becomes excessive in trees over 120 years of age.
The bark beetles are the most important group of insects that attack western white pine. The mountain pine beetle (Dendroctonus ponderosae) kills groups of trees, primarily in mature forests. Trees weakened by blister rust are often attacked by the mountain pine beetle. Likewise, weakened trees are sometimes attacked by the red turpentine beetle (Dendroctonus valens). Usually, this beetle is not aggressive and does not become epidemic, but through repeated attacks it can kill trees. More often, it just weakens them, leading to fatal attack by other bark beetles (12).
Attack of western white pine by mountain pine beetle sometimes results in attack on the bole by emarginate ips (Ips emarginatus). Likewise, the ips beetle (Ips montanus) attacks weakened western white pine, its principal host, in association with other bark beetles. The Pityogenes fossifrons beetle breeds principally in western white pine, but its attacks are seldom primary. The beetle is capable, however, of attacking western white pine reproduction. Many other bark beetles and insects attack western white pine, but, for the most part, they do not cause extensive damage.
Fire Management Considerations
Western white pine is a fire-dependent, seral species. Fire supression
and white pine blister rust have decreased western white pine stocking
from 44 percent in 1941 to 5 percent in 1979 . Periodic,
stand-replacing fire or other disturbance is needed to remove competing
conifers and allow western white pine to develop in early seres
Slash burning: Dry sites in the western white pine forest type respond
poorly to slash burning, while moist sites respond favorably .
Stark  provides information on how to estimate nutrient losses from
the harvest and slash burning of a western white pine stand. The use of
chemical retardent around leave trees in selective cuts has been found
to be effective in reducing cambium damage when slash concentrations are
light or moderate .
For effective fire hazard abatement the recommended Federal slash hazard
index is 11 when planning a prescribed fire in western white pine slash.
An index of less than 9 will provide little reduction, and greater than
12 generates risk of fire escape . Reinhardt and others 
provide information on prescribed fire, slash disposal, duff
consumption, and management considerations after harvest in western
white pine stands in northern Idaho.
Wildlife: Prescribed fire has been recommended in western white pine
stands to maintain areas of abundant browse for elk .
Other: After wildfire it is recommended that salvage operations begin
within the first 2 years . Peterson and Ryan  have developed a
model based on site, fire, and silvicultural information to predict
conifer mortality after wildfire for long-term planning.
Plant Response to Fire
After a stand-replacing fire, western white pine will seed in from
adjacent areas . After a cool to moderate fire that leaves a mosaic
of mineral soil and duff, western white pine will reoccupy the site from
seed stored in the seed bank .
Immediate Effect of Fire
Fire of any intensity will damage the cambium layer of young trees,
usually resulting in death of the tree .
In a mature western white pine stand, a cool fire will kill scattered
trees, while only scarring others. However,the fire scars provide a
vector for butt rots to enter the tree . Moderate to severe fire in
a mature western white pine stand results in cambium damage and
crowning, which usually results in the death of the tree .
The large amount of humus in western white pine forests renders the
trees susceptible to death from heating of the roots .
Tree without adventitious-bud root crown
Initial-offsite colonizer (off-site, initial community)
Secondary colonizer - on-site seed
Secondary colonizer - off-site seed
Mature western white pine, with its moderately thick bark (1.5 inches [3
cm]), moderately flammable foliage, height, and evanescent lower limbs,
is rated moderate in fire resistance [5,11,56]. However, dense stands,
lichen growth, and resinous bark can decrease western white pine's
resistance to fire .
Young trees with their thin bark are very susceptible to lethal damage
by fire .
Western white pine can begin producing strobili at 7 years of age ,
but production can be limited by moisture stress and timing. Moisture
stress in the early summer of the year strobili mature leads to
abortion, while moisture stress in the early summer of the first and
second years prior to strobili emergence causes an increase in the
number of strobili. Moisture stress in the late summer prior to
strobili emergence causes a decrease in strobili numbers .
A good crop of female strobili is about 40 per tree . During fair to
poor crop years cone beetles (Conophthorus spp.), cone moths (Dioryctria
abietivorella and Eucosma rescissorianna), red squirrels, and deer mice
can cause partial or complete crop failures .
Seed production requires 3 years from the onset of bud initiation. Good
seed crops occur every 3 to 4 years. The mean number of seeds per pound
is 27,000 (59,000/kg). The seed can be dispersed by wind up to 2,620
feet (800 m) from the parent tree. Seeds remain viable in the duff for
up to 4 years, but the germination rate decreases. After 2 years the
rate is 25 percent, and after 4 years the rate is 1 percent. Western
white pine's seed requires cold moist stratification of 30 to 120 days
to germinate; germination is epigeal . Moisture and soil
temperature are believed to control the onset of germination. The
perferred germination substrate is mineral soil, but seeds will also
germinate in duff [8,11].
Seedling mortality is quite high in the first year due to snow mold
(Neopeckia coulteri), rodents, late season drought, and elevated soil
temperatures on dry sites . On dry sites seedling establishment is
favored by partial shade, while on moist sites full sunlight favors
Vegetative reproduction: Western white pine does not naturally
reproduce by sprouting or layering. However, cuttings from young trees
treated with rooting hormones (indolebutyric acid) have rooted with fair
success . Williams  describes the process and considerations
for rooting cuttings from older trees (25 years). He obtained a mean
success rate of 37 percent.
Growth Form (according to Raunkiær Life-form classification)
Obligate Initial Community Species
Facultative Seral Species
Western white pine is classified as shade intolerant to very intolerant
. It is usually seral to fir (Abies spp.), spruce (Picea spp.), or
hemlock (Tsuga spp.) [5,9]. Stickney  classified western white pine
as a colonizer.
Western white pine does not respond favorably after release from 30 to
60 years of suppression [5,6].
Reaction to Competition
Western white pine can be regenerated using even-aged silvicultural systems. On favorable sites, clearcut, seed-tree, and shelterwood systems result in adequate and diverse natural regeneration within 5 to 10 years after the regeneration cut. If a natural blister rust-resistant seed source is not present on the site, planting can be used to regenerate the stands.
Western white pine seedlings are well suited for planting. Both bare-root and container-grown western white pine seedlings have excellent survival and growth when properly planted on appropriate sites. Bare-root stock has better survival with spring planting, but containerized stock appears to have excellent survival when planted during either season.
When natural regeneration and the clearcut system are used for establishing conifer mixtures that include western white pine, it is not uncommon to regenerate 11,000 trees per hectare (4,451/acre), of which 1,000/ha (405/acre) are western white pine (4). Similarly, seed-tree cuts can produce 12,000 trees per hectare (4,856/acre) of which 1,500/ha (607/acre) are western white pine. Shelterwood systems produce more trees, but the proportion that are western white pine is less than for other systems. On southerly aspects, regardless of the cutting system, less regeneration occurs.
The individual tree selection system cannot be used to manage western white pine successfully because it tends to favor the more shade-tolerant species, such as western redcedar and western hemlock, but group selection may have limited application.
Where reproduction has become established under partial cuttings, the density of overstory and time until removal greatly affect development. Western white pine growth can be inhibited even by the shade of a light shelterwood. Sixteen-year-old western white pine growing under an overwood density of 6 m²/ha (27 ft²/acre) were 2.0 m (6.6 ft) tall compared to trees 0.5 m (1.6 ft) tall growing under an overwood density of 21 m²/ha (91 ft²/acre) (28).
The composition of a western white pine stand is determined during the first 30 years of the stand's life (13). Lodgepole pine and western larch can grow one and one-half times as fast in height as western white pine during this period. Western larch can usually maintain its superiority in height growth through maturity, but lodgepole pine's growth superiority seldom lasts past age 50. Similarly, grand fir can equal western white pine height growth for the first 30 years and Douglas-fir is about equal in height growth. On northerly aspects and in shaded conditions, western hemlock height growth can equal that of western white pine (8).
Dominant western white pine over age 30 responds to release, but not aggressively. In the Inland Empire, in 55- to 65-year-old stands, half of the basal area must be removed to gain lasting improvement (10). The effectiveness of light to moderate thinnings in 55- to 65-year-old stands of western white pine is short-lived. Therefore, during the first 30 years, species composition is relatively plastic and can be modified materially by changing the density of residual overwood and by weeding or thinning. Beyond age 30, treatments are less effective and must be drastic to be long lasting.
The fungi that have been reported to form mycorrhizae with western white pine are Suillus granulatus, S. subaureus, S. subluteus, Boletellus zelleri, Cenococcum graniforme, Gomphidius ochraceus, G. rutilus, Russula delica, R. xerampelina, and Tricholoma flavovirens.
Life History and Behavior
Height and diameter growth starts from May to late June depending on
elevation, aspect, and latitude .
Strobili buds emerge in June. The buds are differentiated in July and
August of the year preceding emergence. Pollen dispersal lasts for a
mean of 8.5 days and usually starts the last week in June. Time of
flowering varies over a period of 20 days and is strongly controlled by
temperatures during the preceding weeks. It is delayed for 5 days for
every 1,000 feet (300 m) gain in elevation, and 6 days per degree
Fahrenheit below normal temperatures for May and June. The female
strobili ripen from August to September of the second year after bud
The mean phenological development dates for western white pine in
northern Idaho were as follows :
Bark Shoots Buds Pollen Pollen Shoots Winter Cones Cones
Slips Open Burst Starts Ends End Buds Full Open
Apr 28 May 6 May 21 Jun 11 Jun 28 Aug 11 Aug 13 Aug 1 Sep 8
Western white pine is relatively easy to propagate by grafting at all ages (3). Several types of grafts have been used; early spring grafting before flushing has been most successful. Also, scions, taken from a variety of places in the tree crown, graft with equal success. Grafting conducted under greenhouse conditions is more successful than field grafting. Interspecies grafting on other five-needle rootstocks, such as eastern white pine (Pinus strobus), sugar pine (P. lambertiana), and blue pine (P. griffithii), has been generally successful. Grafting of western white pine on species other than the five-needle white pines has not been accomplished.
During the first growing season, a high percentage of seedlings die, principally because of diseases, but insects, rodents, and birds cause serious seedling losses. Fusarium, cause of a damping-off disease, and Neopeckia coulteri, a snow mold, can cause extensive seedling mortality during the first year (15). Seedlings up to 5 years old are often killed by Rhizina undulata, a root rot, in patches 0.5 m (1.6 ft) to 1.5 m (5 ft) in diameter. Seedling mortality late in the first growing season is due primarily to temperature and drought. High surface temperature is the most important cause of mortality on exposed sites, and drought is a factor on heavily shaded areas where root penetration is slow and unable to keep pace with receding soil moisture. For the most part, western white pine seedlings have low drought tolerance (20).
All factors considered, western white pine seedling establishment is favored by partial shade on severe to moderately severe sites. On the more sheltered sites, such as north slopes, little or no shade is best for seedling establishment (28). Once established, western white pine grows best in full sunlight on all sites.
Early root and shoot growth of western white pine seedlings usually is not rapid. The first summer, the primary root grows about 15 cm (6 in) to 30 cm (12 in) in open situations, between 13 cm (5 in) and 23 cm (9 in) under partial shade, and only 5 cm (2 in) to 8 cm (3 in) under full shade. Seedlings planted in soils rich in nutrients, high in organic matter, and with low bulk densities can have first-year root elongation up to 50 cm (20 in). Seedlings usually average between 3 cm (1 in) and 5 cm (2 in) in height by the end of the first growing season. In the Inland Empire, open-grown western white pine seedlings require about 8 years to reach a height of 1.4 m (4.5 ft) (28). Similarly, 20-year-old western white pine grow about 81 cm (32 in) to 99 cm (39 in) per year on good sites and about 23 cm (9 in) to 46 cm (18 in) on poor sites.
Both height growth and diameter growth of western white pine in the Inland Empire usually begin about the first week of May but may begin as early as April 5 and as late as June 25 depending on elevation, latitude, and aspect (24). Also, in the Inland Empire, leaf buds usually open near May 21 but may open as early as March 27 and as late as June 21. Here, shoot growth usually ends by August 11; reported dates for shoot growth cessation are as early as June 9 and as late as October 21. Winter buds can be formed as early as June 14 and as late as September 30 but are usually formed by August 13. In the Inland Empire, diameter growth normally ceases by the end of August. Old needles usually turn straw yellow between the middle of August and the first week of September and drop soon thereafter. Total needle fall of western white pine is moderate when compared to associated species (20), with needle retention of 3 to 4 years.
Seed Production and Dissemination
Western white pines can begin cone production as early as age 7 and become more prolific with age. Not until trees are about age 70 does cone production become both frequent and abundant. It continues to increase with age until trees are about 50 cm (19.7 in) in diameter. After that, seed production depends on individual tree vigor and character of crown or possibly on heritable capacity to set and bear cones (298).
Seed yields for western white pine range from 30,900 to 70,500/kg (14,000 to 32,000/lb) with an average of 59,000/kg (27,000/lb) (17). In the Inland Empire, seed production varies from 41,000 to 457,000/ha (16,600 to 185,000/acre), with average annual seed yields for a 75-year-old stand and an over-mature stand of 8,600/ha (3,500/acre) and 99,000/ha (40,100/acre), respectively.
Several cone and seed insects and rodents can cause partial to almost complete failures of cone crops in otherwise poor to fair crop years. The cone beetles, Conophthorus monticolae and C. lambertianae, and cone moths, Dioryctria abietivorella and Eucosma rescissoriana, cause serious seed losses some years (12). Western white pine seeds are also a favorite food of red squirrels and the deer mouse.
In the Inland Empire, seed dissemination of western white pine begins in early fall; 15 percent of the current crop reaches the ground before September 1, about 85 percent by the end of October, and 15 percent during the late fall and winter (28). Seeds are usually disseminated by wind, but squirrels, mice, and various birds contribute to seed dissemination. Most seeds fall within 120 m (390 ft) of the parent tree, but they have been known to travel over 800 m (2,620 ft) from it (28).
Western white pine seeds remain viable after overwinter storage in duff on the forest floor. Seeds have shown 40 percent viability after one winter's storage, and 25 percent viability after two winters' storage; and less than 1 percent after 3 and 4 years' storage. Western white pine seeds properly stored under artificial conditions of seed moisture content of 5 to 10 percent and temperatures of -18° C (0° F) to -15° C (5° F) remain viable for 20 years (17).
Flowering and Fruiting
The greenish-yellow to bright pink ovulate strobili are borne on stalks at tips of the upper branches, and in the Inland Empire become visible about mid-June of the growing season following initiation of the primordia. The erect conelets are from 1.5 cm to 4.0 cm (0.6 to 1.6 in) long at time of pollen dissemination , and they grow to 2.5 cm to 5.0 cm (1.0 to 2.0 in) long by the end of the first growing season (28).
Time of anthesis may vary over a period of 20 days and is rigidly controlled by temperatures during the weeks immediately preceding anthesis. Anthesis is delayed about 5 days per 300 m (980 ft) increase in elevation, and about 6 days per degree Fahrenheit below normal temperatures for May and June (28). In the Inland Empire, good strobilus crops in western white pine occur every 3 to 4 years, the major cycle being 4 years. Warm, dry "stress" periods, during the early summer of the 2 years before strobilus emergence, favor strobilus production. In contrast, stresses in the late summer of the year prior to emergence or during the period of emergence depress strobilus production. Within individual trees and within localities, maxima pollen shedding and ovulate anthesis practically coincide. No phenological barriers to either selfing or crossing appear to exist, but most western white pine show a moderate to strong discrimination against self-pollination. Western white pine seedlings that result from self-pollination are typically slower growing than seedlings resulting from cross-pollination (3).
Western white pine is predominantly female from first strobilus production at age 7 through age 20 (3). Cultural treatments, such as watering, fertilizing, and cultivating, usually have little effect on this characteristic, but thinning and fertilizing 40-year-old western white pine with nitrogen, phosphorus, and potassium has increased it (1).
Growth and Yield
Tables 1 and 2 show the sizes, net volume, basal areas, and growth rates for western white pine in fully stocked stands in the Inland Empire. Although blister rust modifies stand development, in the absence of the rust, stands develop as shown.
Table 1- Average size and volume of dominant and codominant western white pine growing in fully stocked stands in the Inland Empire Site index at base age 50 years Item 12.2 m or 40 ft 18.3 m or 60 ft 24.4 m or 80 ft Dominants and codominants D.b.h., cm 29.5 41.9 56.9 Height, m 26.8 40.2 53.3 Volume, m³ 0.8 2.2 4.9 Cubic volume,¹ m³/ha 699 976 1,267 Basal area, m²/ha 70 72 74 Dominants and codominants D.b.h., in 11.6 16.5 22.4 Height, ft 88.0 132.0 175.0 Volume, ft³ 27.5 77.0 171.6 Cubic volume, ft³/acre 9,980 13,950 18,100 Basal area,¹ ft²/acre 306 314 322 ¹In trees 0.2 cm (0.6 in) and larger in d.b.h. Table 2- Mean annual increment of fully stocked stands of western white pine in the Inland Empire Site index at base age 50 years Age 12.2 m or 40 ft 18.3 m or 60 ft 24.4 m or 80 ft yr m³/ha 20 0.84 1.40 1.89 40 3.29 4.62 5.95 60 4.90 6.86 8.89 80 5.67 7.84 10.29 100 5.88 8.26 10.78 120 5.81 8.12 10.57 140 5.53 7.70 9.94 yr fbm/acre¹ 20 12 20 27 40 47 66 85 60 70 98 127 80 81 112 147 100 84 118 154 120 83 116 151 140 79 110 142 ¹In trees 0.2 cm (0.6 in) and larger in d.b.h.
Molecular Biology and Genetics
Races Several single recessive genes are recognized in western white pine (3). Albino genes, chlorophyll deficient genes, a curly foliage gene, and a dwarfing gene have been found. Monoterpenes also appear to be under strong genetic control. Height growth gains of 4 to 12 percent are possible according to estimates from progeny testing and selections.
Work on inheritance of blister rust resistance in western white pine began in 1950. This early work indicated considerable heritability of blister rust resistance. Most foliar resistance is governed by genes reducing the frequency of secondary needle infections and causing slow fungus growth in secondary needles (3). In the stem, genetic resistance is governed primarily by genes controlling a fungicidal reaction and causing slow growth of the fungus. Other resistance mechanisms include lowered frequency of needle lesions, premature shedding of needles, and fungicidal reaction in the short shoot. Nursery and field tests of rust resistant seedlings after two cycles of selections indicate rust resistance of 66 and 88 percent, respectively.
Hybrids Western white pine can be easily crossed with other five-needle white pines (3). It hybridizes successfully with Balkan pine (Pinus peuce), blue pine (P. griffithii), eastern white pine (P. strobus), Japanese white pine (P. parviflora), southwestern white pine (P. strobiformis), and limber pine (P. flexilis). Hybridization with Swiss stone pine (P. cembra), Korean pine (P. koraiensis), and whitebark pine (P. albicaulis) has not been as successful.
Barcode data: Pinus monticola
Statistics of barcoding coverage: Pinus monticola
Public Records: 6
Specimens with Barcodes: 7
Species With Barcodes: 1
IUCN Red List Assessment
Red List Category
Red List Criteria
Pinus monticola has a very large extent of occurrence and also a very substantial area of occupancy, both beyond the thresholds for a threatened category. Decline overall is difficult to estimate, but there are estimates of substantial reductions in regeneration in at least one major area (from 44% to 5% between 1941 and 1979) due to competition and pine blister rust. Suppression of fires in the forests is still ongoing, although in national parks and wilderness reserves this is no longer a priority in managing these forests. On the other hand, clear-cutting can benefit regeneration of this species, so it may have increased especially in cut-over areas in British Columbia and elsewhere. This means that the population reduction is likely to be below the threshold for listing as Vulnerable under criterion A4ce, if indeed there is an overall reduction, partly in the past, and projected into the future. The species is therefore listed as Near Threatened.
National NatureServe Conservation Status
Rounded National Status Rank: N4 - Apparently Secure
Rounded National Status Rank: N4 - Apparently Secure
NatureServe Conservation Status
Rounded Global Status Rank: G4 - Apparently Secure
Reasons: Although still considered a fairly common species in many areas of its range, populations of western white pine are affected by white pine blister rust, different species of bark beetles, and susceptible to pole blight from extreme weather conditions. Population declines have been noted since early in the century with a massive dieback in the Pacific region in 1935-1936 triggered by highly anomalous winter weather (Auclair et al 1990). Continuing threats of disease and extremes of climate are still affecting populations, however breeding programs have produced strains that are 65% resistant to white pine blister rust (Griffth 1992). Others consider populations will continue to decline as blister rust infection spreads and intensifies (Tomback 2001).
Environmental Specificity: Broad. Generalist or community with all key requirements common.
Degree of Threat: High
Comments: Although western white pine is a fire-adapted early seral species, trees are susceptible to fire which can damage the cambium layer. This usually results in the death of young trees and the creation of fire scars in older trees. Fire scars can provide an opening for disease, such as butt-rot fungi, to infect a tree. However, fire also removes the humus layer, preparing a favourable seedbed and eliminates competing plants. Large amounts of humus also can cause tree death from heating of the roots (Griffith 1992). White pine blister rust (Cronartium ribicola), dwarf mistletoe (Arceuthobium spp.) and various species of bark beetles also are serious threats affecting populations. Pole blight, a xylem dysfunctional condition related to extreme climatic variation, results in massive cavitation, yellow foliage, crown dieback and the death of many trees. One critical factor with this specific condition was untimely soil frost and winter thaw-freeze cycles, whereas air pollution was determined not to relate to tree dieback for Pinus monticola (Auclair et al. 1990). Weather extremes with climate change may increase the occurrence of this condition in this species.
Biological Research Needs: Continued research for trees resistant to the white pine blister rust infection and the condition of pole blight caused by extreme climate events.
White pine blister rust: The most serious damaging agent of western
white pine is white pine blister rust (Cronartium ribicola) [1,11,23].
This rust was introduced into this country at the turn of the century
from infected seedlings that had been imported from nurseries in France
. White pine blister rust has a life cycle requiring alternate hosts
for its completion: five-needled pines and currants (Ribes spp.). The
rust produces spores on currants that infect white pines. These spores
can be dispersed by wind  up to 10 miles (17 km) . The spores
germinate on the needles, and use the stomatal openings as a vector to
the bole of the tree. This usually results in the death of the host
Breeding programs have produced strains that are 65 percent resistant to
intense exposure to white pine blister rust . Selection of naturally
rust-resistant trees for seed sources for natural regeneration and
planting rust-resistant nursery stock may keep future damage from bister
rust minimal . In established stands that are not rust resistant,
thinning tends to increase the number of new lethal infections, while
pruning tends to decrease the number of new lethal infections .
Fungi: Western white pine is susceptible to three species of needle
cast fungi: Lophodermella arcuata, Lophodermium nitens, and Bifusella
linearis. It is also susceptible to butt-rot fungi, the most important
being Phellinus pini, Phaeolus schweinitzii, and Heterobasidion annosum
The most damaging root disease of western white pine is Armillaria spp.,
which causes fading foliage, growth reduction, dead and rotten roots,
and black rhizomorphs, resulting in weakened or dead trees [11,70].
Annosus root disease (Heterobasidion annosum) also causes some mortality
. It spreads radially, infecting an area up to 0.25 acre (0.1 ha)
away from stumps . Treating freshly cut stumps with borax has been
proven effective in preventing the spread of annosus root disease .
Insects: Western white pine is susceptible to mountain pine beetle
(Dendroctonus ponderosae) and emarginate ips (Ips emarginatus), and is
the principal host for the ips beetle (Ips montanus) .
Pole blight: Pole blight is a physiological disorder brought on by
drought. This disease caused significant mortality from 1935 to 1960.
Tree mortality was believed to have resulted from rootlet mortality,
which reduced western white pine's ability to absorb moisture . The
disease is restricted to sites with shallow soils or soils with low
moisture retention .
Other: Western white pine is sensitive to sulfur dioxide and flouride
smelter fumes. These contaminants cause the foliage to yellow and drop
prematurely. Dwarf mistletoe (Arceuthobium spp.) attacks western white
Silvicultural practices: The method of choice is clearcutting.
Selection cutting is not practical because it favors more shade-tolerant
species. The composition of a western white pine stand is determined in
the first 30 years. Until that time it is fairly plastic, and the stand
can be modified by thinning to enhance western white pine growth .
Planting: Western white pine seedlings are well suited for planting.
Both bareroot and container-grown stock exhibit excellent survival and
growth . When planting seedlings on droughty sites, it is
beneficial to mound the seedbed, as this incorporates organic matter,
increases microbial activity, decreases density, and increases the
moisture capacity of the soil. This results in increased nutrient
availability for seedling growth and increases root penetration .
The soil should be packed lightly around the seedling. This practice
inceases the growth rate in the first year by up to 30 percent .
Seedlings planted in fall have a significantly reduced height growth
compared with those planted in the spring; however, there is little
difference in their survival rates .
Nitrogen can be limiting on some sites after harvest. The application
of nitrogen at 200 pounds per acre (225 kg/ha) has been found to
increase the growth rate of young western white pine stands (less than
10 years old) by 30 percent .
Frost tolerance: When dormant, western white pine is one of the more
frost-tolerant species of the Northwest .
Competitors: Competing vegetation of western white pine can be
effectivly controlled by the application of Roundup herbicide
(isopropylamine salt of glyphosate). The recommended rate of
application is 1 to 3 quarts (1-3 l) of Roundup to 10 gallons (38 l) of
aqueous solution per acre (0.4 ha). This treatment had no observable
effects on western white pine .
Relevance to Humans and Ecosystems
Other uses and values
Native Americans chewed the resin, wove baskets from the bark, concocted
a poultice for dressing wounds from the pitch , and collected the
cambium in the spring for food .
Western white pine forests have aesthetic and recreational value. Cones
of western white pine are collected for novelty items . The tree is
also planted as an ornamental .
Western white pine provides nesting, thermal, and foraging cover for a
variety of aviafauna ; it also provides hiding and thermal cover for
Importance to Livestock and Wildlife
and insects [3,11,64,66]. Western white pine comprises less than 1
percent of the winter diet of elk ; however, it is browsed by
black-tailed deer in the winter when other browse is limited . The
seeds of western white pine are an important part of the diet of red
squirrels and deer mice .
Wood Products Value
straight grained, nonresinous, lightweight, and exhibits dimensional
stability. These qualities render the wood useful in the production of
window and door sashes. The wood is also used in the production of
doors, paneling, dimension stock, matches, and toothpicks . The
dimension stock works well. It takes nails without splitting, and it
takes a nice finish. The wood is also excellent for carving .
pine were listed as follows .
Percent Parts per million
P K Ca Mg S B Zn Fe Mn
0.20 1.10 0.24 0.10 0.09 30 45 45 240
generally rated as poor [3,61,64]. Blue grouse prefer western white
pine needles over those of western hemlock .
Western white pine grows in some of the finest western outdoor recreation areas and has considerable esthetic value. In addition, the long, distinctive cones are collected in considerable numbers for novelties or souvenirs.
Western white pine
Western white pine, Pinus monticola, also called silver pine, and California mountain pine, in the family Pinaceae, is a species of pine that occurs in the mountains of the western United States and Canada, specifically the Sierra Nevada, the Cascade Range, the Coast Range, and the northern Rocky Mountains. The tree extends down to sea level in many areas, particularly in Oregon and Washington. It is the state tree of Idaho, and is sometimes known as the Idaho pine.
Western white pine (Pinus monticola) is a large tree, regularly growing to 30–50 metres (98–164 ft) and exceptionally up to 70 metres (230 ft) tall. It is a member of the white pine group, Pinus subgenus Strobus, and like all members of that group, the leaves ('needles') are in fascicles (bundles) of five, with a deciduous sheath. The needles are finely serrated, and 5–13 centimetres (2.0–5.1 in) long. The cones are long and slender, 12–32 centimetres (4.7–12.6 in) long and 3–4 centimetres (1.2–1.6 in) broad (closed), opening to 5–8 centimetres (2.0–3.1 in) broad; the scales are thin and flexible. The seeds are small, 4–7 mm long, and have a long slender wing 15–22 mm long.
It is related to the Eastern white pine (Pinus strobus), differing from it in having larger cones, slightly longer-lasting leaves (2–3 years, rather than 1.5–2 years) with more prominent stomatal bands, and a somewhat denser and narrower habit. The branches are borne in regular whorls, produced at the rate of one a year; this is pronounced in narrow, stand-grown trees, while open specimens may have a more rounded form with wide-reaching limbs. It is widely grown as an ornamental tree, but has been heavily logged throughout much of its range in the past.
Western white pine (Pinus monticola) has been seriously affected by the white pine blister rust (Cronartium ribicola), a fungus that was accidentally introduced from Europe in 1909. The United States Forest Service estimates that 90% of the Western white pines have been killed by the blister rust west of the Cascades. Large stands have been succeeded by other pines or non-pine species. The rust has also killed much of the Whitebark pine outside of California. Blister rust is less severe in California, and Western white and whitebark pines have survived there in great numbers.
Resistance to the blister rust is genetic, and due to Western white pine's genetic variability some individuals are relatively unaffected by the rust. The Forest Service has a program for locating and breeding rust-resistant Western white pine and sugar pine. Seedlings of these trees have been introduced into the wild.
- Farjon, A. (2011). "Pinus monticola". IUCN Red List of Threatened Species. Version 3.1. International Union for Conservation of Nature. Retrieved 2013-11-10.
- "USDA GRIN Taxonomy".
- Moore, Gerry; Kershner, Bruce; Craig Tufts; Daniel Mathews; Gil Nelson; Spellenberg, Richard; Thieret, John W.; Terry Purinton; Block, Andrew (2008). National Wildlife Federation Field Guide to Trees of North America. New York: Sterling. p. 78. ISBN 1-4027-3875-7.
- Chase, J. Smeaton (1911). Cone-bearing Trees of the California Mountains. Chicago: A. C. McClurg & Co. p. 99. LCCN 11004975. OCLC 3477527. LCC QK495.C75 C4, with illustrations by Carl Eytel - Kurut, Gary F. (2009), "Carl Eytel: Southern California Desert Artist", California State Library Foundation, Bulletin No. 95, pp. 17-20 retrieved Nov. 13, 2011
Western white pine ( Pinus monticola ) is the state tree of Idaho.
Names and Taxonomy
mountain white pine
Idaho white pine
Pinus strobus L. var. monticola (Dougl. ex D. Don) Nutt.
Strobus monticola Rydb.
monticola Dougl. ex D. Don (Pinaceae) [11,38]. There are two recognized
varieties: P. m. var. minima Lemmon and P. m. var monticola .
There are no subspecies or forms.
Western white pine hybridizes with Balkan pine (P. peuce), blue pine (P.
griffithii), eastern white pine (P. strobus), southwestern white pine
(P. strobiformis), and limber pine (P. flexilis) .