Thuja plicata

Cupressaceae -- Cypress family

    Don Minore

    Western redcedar (Thuja plicata), also called Pacific redcedar,  giant-cedar, arborvitae, canoe-cedar, and shinglewood, is the only Thuja  species native to western North America. Extant redcedar volumes are  estimated to be 824 million m³ (29 billion ft³) in British  Columbia (43) and 228 million m³ (8 billion ft³) in the United  States (16). Most of this volume is in mature trees, which have tapered,  often-fluted bases, drooping branches, thin fibrous bark, and small  scalelike leaves arrayed in flat sprays. Many have forked tops. They often  reach ages of 800 to 1,000 years. One particularly large specimen in  Washington has a d.b.h. of 592 cm (233 in), a height of 54.3 m (178 ft),  and a crown spread of 16.5 m (54 ft). The wood is valuable and extensively  used in a wide variety of products.

General: Cypress family (Cupressaceae). Native trees growing to 50 (-75) meters tall, often buttressed at base, with a conical to irregular crown, old individuals frequently with many leaders and many dead spike tops; branches arching, branchlets pendent, flattened, in fan-shaped sprays; bark gray to reddish-brown, 10-25 mm thick, fibrous, separated into flat, connected ridges. Leaves are evergreen, scale-like and sharply pointed, (1-) 3-6 mm long, opposite in alternating pairs (in 4 rows), glossy green above, white-striped on the lower surface, with a spicy fragrance when crushed. Seed cones are ellipsoid, 10-14 mm long, brown; seeds 8-14 per cone, 4-7.5 mm long, with lateral wings about as wide as the body. The common name pertains to the western distribution and cedar-like appearance.

Variation within the species: although small inter-populational differences have been documented, western red-cedar seems to show less within-species genetic variation than other northwestern conifers. Horticultural varieties with color and growth form differences have been developed (atrovirens, fastigiata, pendula).

Distribution: The range of western red-cedar is essentially in two segments: a Coast Range-Cascade Range segment from southeastern Alaska to northwestern California and a Rocky Mountain segment from British Columbia and Alberta to Idaho and Montana. For current distribution, please consult the Plant Profile page for this species on the PLANTS Web site.

Giant arborvitae, western arborvitae, giant red-cedar, Pacific red-cedar, shinglewood, canoe cedar

     AK  CA  HI  ID  MT  OR  WA  AB  BC

Western redcedar occurs along the Pacific Coast from the southern part
of the Alaska Panhandle through British Columbia, western Washington,
and western Oregon, reaching into the coastal redwood forest of northern
California [8,50,54,57].  Inland from the coast it occupies a contiguous
band east of the Cascade Range from central Oregon to southern British
Columbia [54].  Much farther inland a disjunct population occurs along
the west slopes of the Rocky Mountains from Prince George, British
Columbia, to northeastern Washington, northern Idaho, and western
Montana [50,54,57].

More info on this topic.

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
    5  Columbia Plateau
    8  Northern Rocky Mountains

Western redcedar grows along the Pacific coast from Humboldt County, CA  (lat. 40° 10' N.), to the northern and western shores of Sumner  Strait in southeastern Alaska (lat. 56° 30' N.). In California, it is  common only in the lower Mad River drainage and the wet region south of  Ferndale in Humboldt County; it is found elsewhere only in isolated stands  in boggy habitats (19). North of the California-Oregon border, the coastal  range broadens to include the western slopes of the Cascade Range north of  Crater Lake and the eastern slopes north of about latitude 44° 30' N.  (12). Optimal growth and development of western redcedar are achieved near  the latitudinal center of its range- Washington's Olympic Peninsula.

    North of the Olympic Peninsula and Vancouver Island, the coastal range  narrows again and is restricted to the Coast Ranges and offshore islands.  A few scattered stands are found between the Coast Ranges and the Selkirk  Mountains near the southern border of British Columbia, but redcedar's  coastal range is essentially isolated from its interior range.

    The interior range extends south from the western slope of the  Continental Divide at latitude 54° 30' N. in British Columbia through  the Selkirk Mountains into western Montana and northern Idaho (2). The  southern limit is in Ravalli County, MT (lat. 45° 50' N.). With the  possible exception of a few trees east of the Continental Divide near the  upper end of St. Mary Lake, Glacier County, the eastern limit of the range  of redcedar is near Lake McDonald in Glacier National Park, MT.

     
- The native range of western redcedar.

Thuja plicata Donn ex D. Don:
United States (North America)
Canada (North America)
China (Asia)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Alta., B.C.; Alaska, Calif., Idaho, Mont., Oreg., Wash.

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: Limited to Pacific Northwest of North America.

The trees occur on various substrates, commonly on moist sites (swamps, wet ravines, poorly drained depressions), but on a variety of landforms, including rocky slopes, at 0-1500 (-2300) meters elevation. They usually occur in mixed coniferous forests, rarely in pure stands. In cultivation, they prefer moist, acid, well-drained soils but have been grown in heavy clays of the Midwest.

More info for the term: duff

Western redcedar is a large, native, long-lived, evergreen tree
[8,50,57,80].  At maturity it is generally 70 to 100 feet (21-30 m)
tall, sometimes 130 feet (40 m), with a tapering trunk 2 to 4 feet
(0.6-1.2 m) in diameter, sometimes 6 feet (1.8 m) or more.  On some
sites west of the Cascades, old-growth western redcedar often attains
basal diameters of 8 to 10 feet (2.4-3 m) and heights of 200 feet (61
m).  The largest known western redcedars are believed to be 1,000 years
old or more [8].

Western redcedar has a swollen or buttressed base, pointed conical
crown, and horizontal branches curving upward at the tips [80].  The
leaves are scalelike, flattened and 0.05 to 0.1 inches (1.5-3 mm) long.
The twigs are flattened, in fanlike sprays and slightly drooping.  The
bark is thin, fibrous and stringy or shreddy.  Thickness varies from 0.5
to 1 inch (1.3-2.5 cm) [51].  The cones are
clustered near the ends of
twigs and become turned up on short stalks [80].  Western redcedar
retains its lower limbs except when in densely crowded stands [8].

Western redcedar roots are extensive.  Tap roots are poorly defined or
nonexistent, but fine roots develop a profuse, dense network.  Root
systems tend to be shallower and less extensive on wet soils than on
deep, moderately dry soils.  When a thick duff layer is present, many
western redcedar roots lie in the duff rather than in the underlying
soil [50,51].

Tree, Evergreen, Monoecious, Habit erect, Trees without or rarely having knees, Tree with bark rough or scaly, Tree with bark shaggy or peeling, Young shoots in flat sprays, Buds not resinous, Leaves scale-like, Leaves opposite, Non-needle-like leaf margins entire, Leaf apex acute, Leaves < 5 cm long, Leaves < 10 cm long, Leaves not blue-green, Leaves white-striped, Scale leaves without raised glands, Scale leaf glands not ruptured, Scale leaves overlapping, Twigs glabrous, Twigs not viscid, Twigs without peg-like projections or large fascicles after needles fall, Berry-like cones orange, Woody seed cones < 5 cm long, Bracts of seed cone included, Seeds red, Seeds brown, Seeds winged, Seeds equally winged.

Trees to 50(-75) m tall; trunk to 2(-5) m d.b.h., often buttressed at base; bark reddish brown or grayish brown, fibrous, fissured; crown conical; branches arching; branchlets pendulous. Leaves on upper side of branchlets glossy green, (1-)3-6 mm, apex acuminate; lateral leaves longer than facial leaves, apex straight. Pollen cones reddish, 1-3 mm. Seed cones brown, ellipsoid, 1-1.4 cm; fertile cone scales 4-6. Seeds reddish-brown, 4-7.5 mm (including wings).

Trees to 50(--75) m, sometimes stunted in harsh environments; trunk to 2(--5) m diam., often buttressed at base; crown conical. Bark reddish brown or grayish brown, 10--25 mm thick, fibrous, fissured. Branches arching, branchlets pendent. Leaves of branchlets (1--)3--6 mm (sprays sometimes bearing only very small leaves), apex acute, with white markings on abaxial surface when fresh, glossy green on adaxial surface of branchlets. Pollen cones 1--3 mm, reddish. Seed cones ellipsoid, 10--14 mm, brown; fertile scales 2--3 pairs, each with evident, nearly terminal, deltate projection. Seeds 8--14 per cone, 4--7.5 mm (including wings), reddish brown. 2 n = 22.

Thuja gigantea Nuttall.

More info for the terms: fern, natural, organic soils, shrub

Western redcedar grows best in maritime climates with cool, cloudy
summers and wet, mild winters.  In drier areas west of the Cascades,
western redcedar becomes abundant only on wet sites such as ravines,
along streams, or on poorly drained bottomlands.  Near its range limits
in the drier mountains east of the Cascade crest, western redcedar grows
almost exclusively in narrow canyons, where its roots are irrigated all
summer by a mountain stream [8].  In Glacier National Park and the
Selway-Bitterroot Wilderness in Idaho and Montana, western redcedar is
dominant in wet ravines and poorly drained depressions [50].

Precipitation and temperature:  Western redcedar occurs on sites that
receive from 35 inches (890 mm) of annual precipitation to more than 260
inches (6,600 mm), mostly as winter rainfall [50].  Western redcedar is
not resistant to frost and is sometimes damaged by freezing temperatures
in late spring or early autumn.  When sufficient precipitation is
present, low temperatures appear to limit western redcedar's range.  The
northern limits of western redcedar lie between the 52 and 53 degree
Fahrenheit (11.1-11.7 deg C) mean summer temperature isotherms in
southeastern Alaska [50].  Bottomland frost pockets in northern Idaho
are commonly occupied by subalpine fir (Abies lasiocarpa) rather than
western redcedar [51].

Soils:  Western redcedar can tolerate a wide range of soil.  It is found
on all soil textures and parent materials on Vancouver Island.  Coarse
sandy soils are not well suited to the establishment and growth of
western redcedar in northern Idaho and northeast Washington, but rocky
slopes with limited soil development support western redcedars in
southeastern Alaska.  Poorly drained organic soils support redcedar
south of Petersburg, Alaska.  It grows well on shallow soils over chalk
and can tolerate both acid and alkaline soils conditions.  It is able to
survive and grow on soils that are low in nutrients and is found on such
soils over much of its natural range.  However, productivity may be
improved by fertilization [50].

Elevation:  Elevational ranges of western redcedar have been reported as
follows [19,50,51]:

        Alaska - 0 to 3,000 feet (0-910 m)
        British Columbia - 0 to 3,900 feet (0-1,190 m)
        Oregon - 0 to 7,500 feet (0-2,290 m)       
        northern Rocky Mountains - 2,000 to 5,900 feet (610-1,798 m)

In coastal regions, western redcedar is commonly associated with the
following shrub and herb species:  dwarf Oregon grape (Mahonia nervosa),
stink currant (Ribes bracteosum), Alaska blueberry (Vaccinium
alaskaense), box blueberry (V. ovatum), Pacific rhododendron
(Rhododendron macrophyllum), salal (Gaultheria shallon), threeleaf
anemone (Anemone deltoidea), deerfern (Blechnum spicant), slough sedge
(Carex obnupta), and evergreen violet (Viola sempervirens) [50,51].

In interior regions western redcedar is commonly associated with the
following shrub and herb species:  mountain alder (Alnus incana spp.
tenuifolia), Oregon grape (Mahonia repens), common juniper (Juniperus
communis), red raspberry (Rubus idaeus), blue huckleberry (Vaccinium
globulare), Rocky Mountain honeysuckle (Lonicera utahensis), gold thread
(Coptis occidentalis), roundleaf alumroot (Heuchera cylindrica), pine
drops (Pterospora andromedea), and green pyrola (Pyrola chlorantha)
[35,50,51,61].

Common shrub and herb associates of both coastal and interior regions
are as follows:  western serviceberry (Amelanchier alnifolia),
thimbleberry (Rubus parviflorus), oceanspray (Holodiscus discolor),
Devil's club, common snowberry (Symphoricarpos albus), lady fern,
western swordfern (Polystichum munitum), prince's-pine (Chimaphila
umbellata), bunchberry dogwood (Cornus canadensis), false Solomon's-seal
(Smilacina stellata), and Pacific trillium (Trillium ovatum) [50,51].

More info for the terms: association, codominant, series

Western redcedar commonly occurs as a dominant or codominant on
low-elevation moist sites.  In Montana, the western redcedar habitat
type series described by Pfister and others [60] occurs most extensively
in the Swan Valley and Mission Range, extends eastward locally to
Missoula, and forms small riparian stringers along major streams in the
Bitterroot Range west of Hamilton.  Western redcedar occurs as a
riparian dominance type on toe-slope seepages, moist benches, and wet
bottoms adjacent to streams [35].  Daubenmire and Daubenmire [16]
recognized three western redcedar communities in northern Idaho.
Western redcedar/pachistima (Pachistima myrsinites) is an upland
community, while western redcedar/Devil's club (Oplopanax horridus) and
western redcedar/ladyfern (Athyrium filix-femina) occur on bottomlands.
Western redcedar is sometimes found as a codominant with western hemlock
(Tsuga heterophylla) [16,35,60].  Published classifications identifying
western redcedar as a dominant or codominant are as follows:

Old-growth forests of the Canadian Rocky Mountains National Parks [3].
Preliminary plant associations of the southern Oregon Cascade Mountain
  Province [11].
Classification and management of riparian and wetland sites in
  northwestern Montana [13]. 
Forest habitat types of northern Idaho: a second approximation [15].
Forest Vegetation of eastern Washington and northern Idaho [16].
Fire ecology of Lolo National Forest habitat types [17].
Preliminary forest plant association management guide. Ketchikan area,
  Tongass National Forest [18].
Fire ecology of western Montana forest habitat types [21].
A guide to the interior cedar-hemlock zone, northwestern transitional
  subzone (ICHg), in the Prince Rupert Forest Region, British Columbia
  [33].
Riparian dominance types of Montana [35].
Classification and management of riparian sites in southwest Montana
  [36].
Soil classification as an aid to identifying forest habitat types in
  northern Idaho [54].
Forest habitat types of Montana [60].
Reference material Daubenmire habitat types [77].
Preliminary forest plant associations of the Stikine area, Tongass
  National Forest [78].
A study of the Vegetation of southeastern Washington and adjacent Idaho
  [81].

More info on this topic.

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):

   FRES20  Douglas-fir
   FRES21  Ponderosa pine
   FRES22  Western white pine
   FRES23  Fir - spruce
   FRES24  Hemlock - Sitka spruce
   FRES25  Larch
   FRES26  Lodgepole pine
   FRES27  Redwood
   FRES28  Western hardwoods

More info on this topic.

This species is known to occur in association with the following cover types (as classified by the Society of American Foresters):

   210  Interior Douglas-fir
   212  Western larch
   213  Grand fir
   215  Western white pine
   218  Lodgepole pine
   221  Red alder
   222  Black cottonwood - willow
   223  Sitka spruce
   224  Western hemlock
   225  Western hemlock - Sitka spruce
   226  Coastal true fir - hemlock
   227  Western redcedar - western hemlock
   228  Western redcedar
   229  Pacific Douglas-fir
   230  Douglas-fir - western hemlock
   231  Port-Orford-cedar
   232  Redwood

More info on this topic.

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
   K006  Redwood forest
   K012  Douglas-fir forest
   K013  Cedar - hemlock - pine forest
   K014  Grand fir - Douglas-fir forest
   K015  Western spruce - fir forest

Western redcedar can tolerate a wide range of soil proper-ties in most  localities. Soils on which it is most commonly found are in the orders  Inceptisols, Ultisols, and Histosols. It is found on all landforms, soil  textures, and parent materials on Vancouver Island (39). In southwestern  Oregon, it grows on sedimentary, metasedimentary, gabbroic, dioritic,  granodioritic, and occasionally even serpentinite and peridotite parent  materials (24). Coarse sandy soils are not well suited to establishment  and growth of redcedar in northern Idaho and northeastern Washington, but  rocky slopes with limited soil development support redcedars in  southeastern Alaska. Poorly drained organic soils also support redcedar  south of Petersburg, AK. It grows on loams, clays, sands, chalk downland,  and Molina-Juncus peat in England, but is most competitive on  fine-textured lowland soils there. It grows well on shallow soils over  chalk and can tolerate both acid and alkaline soil conditions (45).

    Western redcedar seems able to survive and grow on soils that are low in  nutrients and is found on such soils over much of its natural range. Site  index is positively correlated with foliar nitrogen, sulfur, copper,  boron, and chlorophyll. However, productivity may be improved by  fertilization (44). When grown in well watered soil fertilized with  nitrogen, phosphorus, and potassium, redcedar seedlings outgrow the  seedlings of Douglas-fir (Pseudotsuga menziesii), grand fir (Abies  grandis), Sitka spruce (Picea sitchensis), western hemlock,  and ponderosa pine (Pinus ponderosa). Available nitrogen,  calcium, and water appear to be the most important factors affecting  growth and establishment of redcedar. Established redcedars tend to raise  soil cation exchange capacities, pH's, and amounts of exchangeable calcium  (1) and thus benefit the soils in which they grow.

    Western redcedar grows from sea level to 910 m (3,000 ft) in  southeastern Alaska. In British Columbia, the elevational range is  higher-from sea level to 1190 m (3,900 ft). Redcedar is found in the  interior from 320 m (1,050 ft) to 2130 m (7,000 ft).

    The greatest range in elevation occurs in Oregon, where the species  occurs from sea level to 2290 m (7,500 ft) at the rim of Crater Lake.

Coastal western redcedar receives from less than 890 mm (35 in) of  annual precipitation to more than 6600 mm (260 in), mostly as winter  rainfall; interior western redcedar, about 710 mm (28 in) in the north,  810 to 1240 mm (32 to 49 in) farther south-about half as spring and autumn  rain, one-third as winter snow (2).

    Although western redcedar is abundant in many forested swamps, it is  sometimes found on sites that are too dry for western hemlock (Tsuga  heterophylla) (12,39,42), probably because the root penetration of the  redcedar is better. Redcedar leaves are not protected from excessive  transpiration by cutin and wax.

    Trees tolerate stagnant winter water tables averaging less than 15 cm (6  in) below the soil surface on the Olympic Peninsula (32). The species  dominates wet ravines and poorly drained depressions in both Glacier  National Park in Montana and the Selway Bitterroot Wilderness in Idaho  (20,21).

    Where sufficient precipitation is present, low temperature appears to  limit the species' range. Length of the frost-free period abruptly  decreases just above the tree's upper elevation limits on Vancouver  Island. The northern limits of western redcedar lie between the 11.1°  and 11.7° C (52° and 53° F) mean summer temperature  isotherms in southeastern Alaska. Absolute minimum temperatures  experienced by western redcedar in British Columbia are -10° to -30°  C (14° to -22° F) in coastal populations, -14° to -47°  C (7° to -53° F) in the interior (28). Western redcedar has a  growing season of at least 120 frost-free days along the coast but as few  as 75 frost-free days in some portions of its interior range. It is not  resistant to frost and is sometimes damaged by freezing temperatures in  late spring or early autumn.

On various substrates, commonly in moist sites, mixed coniferous forests, usually not in pure stands; 0--1500(--2000)m.

Systems

• Terrestrial

Comments: Wet coastal forests.

Cultivated. Jiangsu, Jiangxi [native to W Canada, NW United States]

Cone production begins in open-grown trees of western red cedar at about 10-20 years of age but peak production occurs after 70-80 years and may continue for several centuries. Good seed crops are produced at intervals of 2-3 years.

In clearcuts and other disturbed areas, seedlings account for most of the western red-cedar regeneration, but seedlings in mature stands may be less abundant than individuals produced by vegetative reproduction from layering, rooting of fallen branches, and branch development on fallen trees. Disturbed mineral soil seems to be a major requirement for regeneration from seed. Unburned soil provides better seedbed than scorched soil, but slash burning may create mineral soil surfaces in cut-over areas. In mature stands of western red cedar, rotten wood in contact with the soil provides an effective seedbed. Partial shade, which lowers evaporation and soil temperature, is beneficial to seedling growth.

Western red cedar is often present in pioneer, seral, and climax stages of forest succession. Vegetative regeneration may be predominant in ecologically stable communities, but wide seed distribution allows it to invade disturbed areas. It is highly shade-tolerant and is well suited for reforesting high brush-risk areas near the coast.

Age determination of western red-cedar is complicated by buttress formation and the associated complex growth patterns, but ring counts of trees from Washington and British Columbia indicate that some trees live at least up to 1460 years.

In Great Britain and/or Ireland:
Foodplant / pathogen
Armillaria mellea s.l. infects and damages Thuja plicata

Foodplant / saprobe
immersed, opening by little lids apothecium of Didymascella thujina is saprobic on dead, attached leaf of Thuja plicata
Remarks: season: 6-8

Foodplant / saprobe
immersed acervulus of Truncatella coelomycetous anamorph of Truncatella hartigii is saprobic on bark of Thuja plicata

Pure stands of western redcedar cover some small areas, but it is  usually associated with other tree species. Along the coast these include  black cottonwood (Populus trichocarpa), bigleaf maple (Acer  macrophyllum), western hemlock, mountain hemlock (Tsuga  mertensiana), Sitka spruce, western white pine (Pinus monticola),  lodgepole (shore) pine (P. contorta), Port-Orford-cedar (Chamaecyparis  lawsoniana), Alaska-cedar (C. nootkatensis), incense-cedar  (Libocedrus decurrens), Douglas-fir, grand fir, Pacific silver fir  (Abies amabilis), red alder (Alnus rubra), Pacific madrone  (Arbutus menziesii), and Pacific yew (Taxus brevifolia). Several  of these species (black cottonwood, western hemlock, western white pine,  Douglas-fir, grand fir, and Pacific yew) are also associated with western  redcedar in the interior. Subalpine fir (Abies lasiocarpa), western  larch (Larix occidentalis), Engelmann spruce (Picea  engelmannii), white spruce (P. glauca), lodgepole pine, and  ponderosa pine are also associated with redcedar in the interior.

    Redcedar is a major component of two forest cover types (11): Western  Redcedar (Society of American Foresters Type 228) and Western  Redcedar-Western Hemlock (Type 227). It is a minor component of the  following types:

    210  Interior Douglas-Fir 
212  Western Larch 
213  Grand Fir 
215  Western White Pine 
218  Lodgepole Pine 
221  Red Alder 
222  Black Cottonwood-Willow 
223  Sitka Spruce 
224  Western Hemlock 
225  Western Hemlock-Sitka Spruce 
226  Coastal True Fir 
229  Pacific Douglas-Fir 
230  Douglas-Fir-Western Hemlock 
231  Port-Orford-Cedar 
232  Redwood

    Some associated shrub species are listed in table 1. Several occur in  both interior and coastal environments, but Rocky Mountain honeysuckle  (Lonicera utahensis) and clematis (Clematis columbiana) are  associated with redcedar only in the interior, whereas salmonberry (Rubus  spectabilis) and red huckleberry (Vaccinium parvifolium) are  found only on the Pacific slope. Pacific rhododendron (Rhododendron  macrophyllum) is an abundant associate in coastal California, Oregon,  and Washington, but it is rare and confined to isolated locations in  south-coastal British Columbia. Salal (Gaultheria shallon) also is  an abundant associate. Its range extends farther south than that of  redcedar, but the northern limits of salal are nearly the same as the  northern limits of western redcedar in coastal Alaska.

    Table 1- Shrub species often associated with western  redcedar in coastal and interior portions of its native range.          Coastal    Interior    Both Coastal and Interior            Oregongrape    Mountian alder    Western serviceberry        (Berberis nervosa)      (Alnus tenuifolia)      (Amelanchier alnifolia)      Stink currant    Creeping western barberry    Rustyleaf menziesia        (Ribes bracteosum)      (Berberis repens)      (Menziesia ferruginea)      Alaska blueberry    Common juniper    Thimbleberry        (Vaccinium alaskaense)      (Juniperus communis)      (Rubus parviflora)      Box blueberry    Cascade azalea    Oceanspray        (Vaccinium ovatum)      (Rhododendron albiflorum)      (Holodiscus discolor)      Red huckleberry    Red raspberry    Devilsclub        (Vaccinium parvifolium)      (Rubus idaeus)      (Oploponax horridum)      Salmonberry    Blue huckleberry    Pachistima        (Rubus spectabilis)      (Vaccinium globulare)      (Pachistima myrsinites)      Pacific rhododendron    Rocky Mountain honeysuckle    Baldhip rose        (Rhododendron macrophyllum)      (Lonicera utahensis)      (Rosa gymnocarpa)      Salal    Clematis    Common snowberry        (Gaultheria shallon)      (Clematis columbiana)      (Symphoricarpos albus)              Ovalleaf huckleberry                (Vaccinium ovalifolium)              Some associated herb species are listed in table 2. Many are common in  both coastal and interior environments. However, slough sedge (Carex  obnupta) and Pacific water-parsley (Oenanthe sarmentosa) are  limited to moist habitats west of the Cascades, whereas wild sarsaparilla  (Aralia nudicaulis) and goldthread (Coptis occidentalis) occur  with redcedar only in the interior.

    Table 2- Herb species often associated with western  redcedar in coastal and interior portions of its native range.          Coastal    Interior    Both Coastal and Interior            Threeleaf anemone    Goldthread    Maidenhair fern        (Anemone deltoidea)      (Coptis occidentalis)      (Adiantum pedatum)      Deerfern    Everlasting corydalis    Ladyfern        (Blechnum spicant)      (Corydalis sempervirens)      (Athyrium filix-femina)      Slough sedge    Malefern    Western swordfern        (Carex obnupta)      (Dryopteris filix-mas)      (Polystichum munitum)      Pacific water-parsley    Largeleaf avens    Mountain woodfern        (Oenanthe sarmentosa)      (Geum macrophyllum)      (Dryopteris austriaca)      Oregon oxalis    Roundleaf alumroot    Prince's-pine        (Oxalis oregana)      (Heuchera cylindrica)      (Chimaphila umbellata)      Dwarf blackberry    Panicle bluebells    Bunchberry        (Rubus lasiococcus)      (Mertensia paniculata)      (Cornus canadensis)      Youth-on-age    Pine drops    Skunkcabbage        (Tolmiea menziesii)      (Pterospora andromedea)      (Lysichitum americanum)      White inside-out-flower    Green pyrola    False Solomon's-seal        (Vancouveria hexandra)      (Pyrola chlorantha)      (Smilacina stellata)      Evergreen violet        Pacific trillium        (Viola sempervirens)          (Trillium ovatum)              Coastal redcedar plant communities in British Columbia have been  classified into 24 associations under 9 alliances in the Thuja-Rubus  spectabilis order (35). Communities listed in less detailed coastal  classifications include redcedar/swordfern, redcedar/devilsclub/maidenhair  fern, redcedar/maidenhair fern-ladyfern, redcedar-western  hemlock/devilsclub/ladyfern, redcedar-grand fir/mountain boxwood,  redcedar-grand fir/swordfern, redcedar-Douglas-fir/Oregongrape,  redcedar-Sitka spruce-red alder/skunkcabbage-slough sedge, and  redcedar/skunkcabbage (12,28).

    The redcedar/skunkcabbage plant community also occurs in the interior;  where redcedar/devilsclub, redcedar/devilsclub/coolwort (Tiarella  trifoliata), redcedar/queenscup (Clintonia uniflora), and  redcedar/maidenhair fern are found (7,28,42).

Western redcedar is less susceptible than its  associates to most damaging agents, but, as it is longer lived, damaged  trees are common. Although they are as windfirm as Douglas-fir on dry  sites, redcedars, are often windthrown in wet environments and are not  resistant to windthrow on the moist sites where growth and yield are  highest. Fire resistance also varies with environment. Redcedar is more  severely damaged by fire than any of its associates along the coast but is  less susceptible than Engelmann spruce, western hemlock, and subalpine  fir in the interior (30).

    Western redcedar suffers little damage from insects, but it is a host  for several economically important insect species (13). One of the most  important is the gall midge, Mayetiola thujae, which sometimes  seriously damages redcedar seeds in Oregon, Washington, and British  Columbia. Newly planted seedlings are occasionally damaged by a weevil  (Steremnius carinatus) in British Columbia, and larger trees are  killed by a bark beetle (Phloeosinus sequoiae) on poor sites in  southeastern Alaska. The western cedar borer (Trachykele blondeli)  causes degrade and cull in sawtimber.

    More than 200 fungi are found on western redcedar, but it is less  susceptible to pathological attacks than are most of its associates.  Indeed, redcedar may be a suitable alternative species on coastal  Douglas-fir and western hemlock sites where soils are infected with Phellinus  weiri, Fomes annosus, or Armillaria spp.(37).  Nevertheless, many attacks occur during the long lives of some redcedar  trees, and the heartwood extractives that provide decay resistance are  eventually detoxified through biodegradation by a series of invading fungi  (25). As a result, the volume of accumulated decay in living trees is  greater for western redcedar than for any other major conifer in British  Columbia (25), and hollow old trees are common in the interior (7).

    The major seedling disease, Didymascella thujina, is a leaf  blight that infects 2nd- and 3rd-year nursery seedlings. As much as 97  percent of the natural redcedar reproduction may also be killed when this  blight reaches epidemic proportions (2). Epidemics are rare in North  America, however, and Didymascella is not as damaging here as it  is in Europe, where the disease seriously limited production of planting  stock until cycloheximide fungicides were developed (3,52).

    In North America, the most important fungi attacking redcedar are root,  butt, and trunk rots (23). The root and butt rots include Phellinus  weiri, Armillaria mellea, and Poria subacida. Poria asiatica and  P. albipellucida are the most important trunk rots near the coast;  P. asiatica and Phellinus weiri are most important in the  interior range of western redcedar (2). These rots are most evident in old  stands, where much of the standing volume is often defective and  unmerchantable.

    Redcedar seedlings and saplings are often severely browsed by deer, elk,  or rodents, and browse damage may be the most important  stand-establishment problem (6).

    Western redcedar is damaged more than Sitka spruce by salt spray. Its  foliage is more severely damaged by sulfur dioxide than is the foliage of  Douglas-fir, western hemlock, and Sitka spruce and less damaged than the  foliage of subalpine fir and grand fir. Redcedar is damaged less than  Douglas-fir by airborne fluorides and ozone (30).

More info for the terms: duff, fuel, tree

Riparian stringers supporting western redcedar may act as firebreaks
because the moist duff does not readily burn [21].  Old-age western
redcedar stands have heavy fuel loads, but a large proportion of this
material is in the form of deep duff layers and downed, rotting log
material.  These stands could support slow moving fires at best; once
ignited, however, such heavy fuel materials could support long-lasting
fires [29].
 
Fire-killed western redcedar often shows little deterioration even after
5 years.  The bark usually remains intact on dead tree for 5 years.
Fire mortality produces no immediate reduction in strength of western
redcedar poles, and some large trees remain salvageable for almost 100
years after being killed by fire [51].

When slash from decadent western redcedar-western hemlock stands was
burned, a greater proportion of western redcedar than of western hemlock
slash was consumed.  This was a result of greater longitudinal and
horizontal fracturing of the western redcedar.  When fracturing does not
occur, western hemlock slash is at least as flammable as western
redcedar slash.  Fire spreads faster in western redcedar when the slash
from both species is 1 year old.  Western redcedar slash does not drop
its foliage.  The slash of western redcedar is less flammable when
chipped.  One study showed that the fire hazard normally associated with
cutting of western redcedar poles was reduced by skidding entire
pole-size trees to the landing, where the slash was chipped and blown
over the edge [51].

Slash from western hemlock-western redcedar-Alaska-cedar forests produce
greater nutrient losses to the atmosphere when the slash composition has
a greater proportion of Alaska-cedar and western redcedar.  One can
expect smaller nutrient losses when western hemlock makes up the
majority of the slash [23].  For further details on slash burning of
western redcedar refer to the fire case study in the Alaska-cedar Fire
Effects Information System species review.

More info for the term: prescribed fire

Hamilton's Research Papers (Hamilton 2006a, Hamilton 2006b) provide
information on prescribed fire and postfire response of plant
community species, including western redcedar, that was not available when
this species review was originally written.

More info for the term: duff

Western redcedar is commonly killed by fire.  Because of their large
size, however, old western redcedar trees can often survive if they are
not completely girdled by fire [21].  Shallow roots under the duff layer
are often scorched when the duff layer burns and even surface fires may
kill western redcedar [51].  Fire injury to roots can lead to fungal
infection, chronic stress, and growth losses [65].  The most common
causes of fire mortality are root charring and crown scorching [70].

More info for the terms: secondary colonizer, tree

   Tree without adventitious-bud root crown
   Secondary colonizer - off-site seed

More info for the terms: fire interval, fire regime, frequency, mean fire interval, resistance

Western redcedar fire resistance is low to moderate [21].  Its thin
bark, shallow root system, low dense branching habit, and highly
flammable foliage make it susceptible to fire damage [21,59].  However,
it often survives fire because of it large size [21].  Old western
redcedar trees are commonly fire scarred in northern Idaho [51].
Western redcedar is more severely damaged by fire than any of its
associates along the coast region but is less susceptible than Engelmann
spruce (Picea engelmannii), western hemlock, and subalpine fir in
interior regions [50].

The frequency of fire in western redcedar stands tends to be low
[13,73].  In most of the western redcedar forests from southern British
Columbia to northern California moderate to severe wildfires occur at
long intervals between 50 to 350 years [10].  In streamside and seepage
areas dominated by western redcedar the mean fire interval is greater
than 200 years.  In western redcedar habitats on lower and middle slopes
the mean fire interval is 50 to 150 years [82].  In the
Selway-Bitterroot Wilderness those stands dominated by western redcedar
had the longest fire regime [29].

More info on this topic.

More info for the terms: climax, competition, tree

Obligate Climax Species

Western redcedar is very shade tolerant [8,21,50,51].  It is one of the
most shade tolerant species growing in cedar-hemlock ecosystems of the
northern Rocky Mountains [25].  It is usually considered a climax or
near climax species, but it can be found in all stages of forest
succession.  It invades disturbed areas as widely distributed seeds but
regenerates vegetatively in undisturbed areas, tolerating competition in
both [50].  Moisture and soil conditions strongly influence the
successional status of western redcedar.  It is climax on wet sites in
the Lake McDonald region of Glacier National Park and on calcium-rich
seepage habitats in British Columbia [51].  In Glacier National Park,
western redcedar enters pioneer communities.  The seedlings develop
rapidly in open stands of lodgepole pine (Pinus contorta) and western
larch (Larix occidentalis)[32].  It can survive as a late-seral or
coclimax tree on western-hemlock-dominated sites [21].  In Idaho,
western white pine (P. monticola) stands are slowly replaced by a
western hemlock-western redcedar climax [51].

More info for the terms: climax, competition, duff, epigeal, layering, resistance, shrubs, tree

Seed production and dissemination:  Western redcedar reproduces from
seeds more readily in open, disturbed areas, such as clearcuts, than in
undisturbed stands [19].  Seed production normally begins when trees are
20 to 30 years old [73].  However, open-grown trees may produce seed by
age 10 [19,50].  Cones average about three to six seeds, but cones are
often numerous and heavy seed crops are common.  Average annual seed
crops vary from 100,000 to 1,000,000 seeds per acre
(247,000-2,470,000/ha) in coastal forests and from 22,000 to 111,000 per
acre (54,000-274,000/ha) in the interior [50].  Pure stands of western
redcedar may yield 60,704,168 seeds per acre (150,000,000/ha).  Poor
cone crops are rare [19].  Large seed crops occur every 3 to 4 years
[19,51].

Western redcedar seeds are small, 203,000 to 592,000 seeds per pound
(448,000-1,305/Kg) [8,50].  The seeds are dispersed primarily by wind.
However, the seeds have small wings and are not carried more than 400
feet (122 m) from the parent tree [8,48,50].

Germination:  Germination is epigeal.  Western redcedar seeds germinate
well without stratification and remain viable for at least 7 years
stored dry (5 to 8 percent moisture) at 0 degrees Fahrenheit (-18 deg C)
[50].  Stratification may improve the germination of some dormant seed
lots.  However, in others it may lower the germination capacity [51].
Haig [34] reported germination rates of 73 percent, and Schopmeyer [69]
reported germination rates of 34 to 90 percent.

Mineral soil has been found to be a better seedbed in many environments
than moss or duff, which may dry out rapidly [19,21,50].  Heavily shaded
seedbeds have been associated with the best germination of western
redcedar in British Columbia [19].  Rotten wood that is in contact with
the soil is the preferred seedbed in old western redcedar groves [50].
Graham [26] found that germination was best on burned surfaces.
 
Seedling development:  Western redcedar seedling survival is low [8,50].
Drought and high soil temperatures damage seedlings grown in full
sunlight [8,40].  Fungi, birds, insects, and smothering by fallen leaves
of deciduous shrubs are some other causes for the high mortality of
western redcedar seedlings [8,19].  Seedlings grow best in partial
shade, although they may fail on heavily shaded sites due to poor root
penetration [19].  Seedlings show high resistance to root flooding [47]
and respond well to removal of competition [57].  In one study, removal
of shrubs resulted in an increase in height growth of western redcedar
compared to unreleased trees [26].

Of all conifers in the northern Rocky Mountains, western redcedar and
western hemlock seedlings grow the slowest.  Annual height growth of
western redcedar seedlings is highly variable, from less than 0.39
inches (1 cm) in dense stands to over 7.5 inches (19 cm) in thinned
stands [26].

Vegetative reproduction:  Communities with closed canopies favor
vegetative reproduction over sexual reproduction [32].  Western redcedar
generally relies on vegetative reproduction in climax old-growth stands
with high soil moisture throughout the growing season [21,27].  The
frequent absence of adequate moisture in the upper soil layers of
well-drained sites often is responsible for western redcedar's reduced
ability to vegetatively reproduce on upland sites [28].  Three natural
types of vegetative reproduction occur:  (1) layering, (2) rooting of
fallen, living branches that have been torn off by wind or snow and have
fallen on wet soil; and (3) rooting along the trunks of fallen, living
trees [19,32,58].

More info on this topic.

More info for the term: phanerophyte

  
   Phanerophyte

More info for the term: tree

Tree

After fire, western redcedar will readily establish on bare mineral soil
seedbeds via off-site wind dispersed seeds [22,26].  Although unburned
soil benefits western redcedar regeneration more than soil that has been
scorched, slash burning favors western redcedar by creating more mineral
soil surfaces in cutover areas [50].

Only Pacific silver fir, western  hemlock, and Pacific yew are more tolerant of shade than western redcedar  (30). Its relative tolerance may be higher in warm than in cool areas, but  redcedar is very tolerant wherever it grows, and it may be "the  species of choice" for reforesting high, brush-risk areas near the  coast (6). Often present in all stages of forest succession, redcedar  occupies pioneer, seral, and climax positions (39). Multiple attributes  seem to be responsible-redcedar invades disturbed areas as widely  distributed seeds but regenerates vegetatively in undisturbed areas,  tolerating competition in both (26). Nevertheless, it is usually  considered a climax or near climax species.

    Western redcedar is best managed on moist sites characterized by the  presence of ladyfern, queenscup, mountain woodfern, oakfern (Gymnocarpium  dryopteris), or thimbleberry. On poorly drained sites of lower  quality, fertilizing with nitrogen appears to benefit growth (37). Urea  seems to be a better source of that nitrogen than ammonium nitrate (54).  Redcedar can be grown in stands of mixed species where uneven-aged  management is practiced or when redcedar poles are to be produced under  normal even-aged management regimes. But pure stands are more suitable for  the long rotations needed to produce large sawtimber, shingles, and  shakes.

    Where western redcedar is managed in mixed-species or uneven-aged  stands, its excellent shade tolerance and long life should be considered.  Redcedar is usually overtopped by Douglas-fir, grand fir, western hemlock,  and western white pine. It tolerates understory conditions in  mixed-species stands but often grows slowly there. In uneven-aged stands,  western redcedar can maintain acceptable growth rates over long periods,  but it should not be given excessive crown space. Thinning from above may  release the redcedars in mixed-species stands; thinning from below is  preferable in uneven-aged stands of western redcedar. In the northern  Rocky Mountains, growth response to release is best on large, young  redcedars with green-yellow foliage growing on northerly aspects (17).  Redcedars probably should not be released when overtopped, however,  because much of the increased growth after their release often occurs in  large branches and a spreading crown rather than stem wood (37).

    Most western redcedars are harvested by clearcutting the mixed-species  stands in which they grow. Because of steep terrain, decay, and breakage,  redcedar harvesting costs are high and lumber recovery is low (55).  Redcedars should not be left as scattered seed trees, however; even those  along clearcut margins may be lost to windthrow or exposure. Effects of  slash-burning vary with site conditions, but low-impact spring burns tend  to benefit the mycorrhizal colonization of seedlings (6).

Tree roots are extensive. Redcedars made up only  17 percent of the basal area but accounted for 82 percent of the root  length in a mixed-species stand in northern Idaho (29). Tap roots are  poorly defined or nonexistent, but fine roots develop a profuse, dense  network.

    Western redcedar roots usually are deeper than the roots of western  hemlock but shallower than the roots of western larch, western white pine,  grand fir, and Douglas-fir (30). The soils on which these species usually  grow may be responsible, however, because western redcedar, western  hemlock, and Douglas-fir trees of similar size growing on similar soils  have roots that penetrate to similar depths and extend over similar areas  (10). Shallow root systems are most frequent where soil bulk density is  high. Redcedar roots cannot grow in dense soils penetrated by the roots of  Douglas-fir, red alder, lodgepole pine, and Pacific silver fir (30).  Redcedar root systems also tend to be shallower and less extensive on wet  sites than they are on deep, moderately dry soils.

    Where a thick duff layer is present, many redcedar roots lie in the duff  rather than in the underlying soil. Root grafting is common (9). Western  redcedar mycorrhizae are of the vesicular-arbuscular type, and redcedar  seedlings are more responsive to mycorrhizal inoculation than are the  seedlings of redwood (Sequoia sempervirens), incense-cedar (Libocedrus  decurrens), and giant sequoia (Sequoiadendron giganteum) (27).

More info on this topic.

More info for the term: phenology

The reproductive cycle of western redcedar occurs over approximately 16
months.  Phenology varies between coastal and interior regions.  For
trees in the middle of the coastal distribution on Vancouver Island,
pollen and seed cones develop in early June.  Pollen forms in late
February or early March of the second season.  Pollination occurs within
1 to 2 weeks usually in March but may begin as early as mid-February in
mild coastal areas or as late as early April at higher elevations.
Pollination in March is most common [57].  Fertilization occurs in late
May.  Cones mature in October.  West of the Cascade Range, cone maturity
is usually reached in 5 months, but in northern Idaho it takes 3 months.
Major seedfall occurs during October and November in both the interior
and coast range [50].  Dry warm weather can cause earlier seed release.
Some seeds may be retained in the cones and gradually shed throughout
the winter [19].  Where moisture and temperature conditions are
favorable, germination can occur in the autumn, winter, or spring [50].
Along the coast region, seeds generally germinate in either fall or
spring [8].

Three types of natural vegetative  reproduction occur: layering, rooting of fallen branches, and branch  development on fallen trees. The resulting "veglings" are more  abundant than seedlings in mature Idaho stands (40). Saplings that have  been knocked down in the western Cascades often regenerate when their  branches root.

    Redcedar clones are easily propagated by the rooting of stem cuttings.  Although untreated cuttings will root, a 1-minute dip in a 3,000 ppm  solution or a 4-hour soak in a 200 to 400 ppm solution of indolebutyric  acid improves rooting speed, the number of cuttings rooted, and the total  length of roots per cutting. Ramets for seed orchards can be produced by  treating cuttings with indolebutyric acid, then rooting them in a 1-to-1  mixture of peat and perlite (8). Young fragmented stems can be induced to  bud after being soaked in a cytokinin solution, and the resulting buds can  be rooted on a culture medium that contains napthalineacetic acid and  kinetin (33).

Most seeds escape rodent and bird  predation, but seedling mortality is high during the germination period  (15). Where moisture and temperature conditions are favorable, germination  can occur in the autumn, winter, or spring. Almost no germination occurs  after the first year, however. Seedbed quality may be critical.

    Throughout the range of western redcedar, disturbed mineral soil  seedbeds seem to be a major requirement for regeneration from seed (41).  Although unburned soil benefits redcedar more than soil that has been  scorched, slash burning favors redcedar by creating more mineral soil  surfaces in cutover areas. Rotten wood that is in contact with the soil is  the preferred seedbed in old redcedar groves (41). Partial shade is  beneficial because drought and high soil temperature damage seedlings in  full sunlight, and poor root penetration causes damage from drought in  full shade (48).

    Direct seeding in the autumn is successful where soil moisture is  available, but large quantities of seed may be required to obtain adequate  stocking. In the nursery, spring sowing is best; half-shaded seedbeds are  recommended (47). Pelleting the seeds makes them more compatible with  automated nursery sowing machinery (8). Containerized nursery seedlings  can be produced in 7 months. They survive as well or better than bare-root  stock when planted in coastal Oregon, Washington, and British Columbia,  but 2-year-old bare-root stock tends to be most cost effective in the  coastal range (6). When bare-root stock is planted, recently lifted  dormant seedlings with low shoot/root ratios should be used and cold  storage avoided whenever possible. Containerized stock planted in the  spring appears to perform better than bare-root stock in the interior  (18). Natural regeneration is important in the northern Rocky Mountains,  where it is most frequently successful on westerly and northerly aspects  in western redcedar habitat types (18).

    Western redcedar seedlings are less tolerant of high soil temperature  and of frost than are the seedlings of Engelmann spruce, grand fir, and  Douglas-fir. The exposed upper foliage of young redcedars often sunburns  severely (31). Roots of seedlings grow more slowly than the roots of  Douglas-fir and incense-cedar, but they outgrow the roots of seedling  western hemlock and Sitka spruce. Shoots have a longer growth period than  any associated conifer. Non-rigid leaders are produced, and neither  lateral nor terminal shoots form dormant buds. Lateral shoot growth is  vigorous, amounting to at least 80 percent of terminal shoot growth in  young redcedars (31). Seedlings account for most of the western redcedar  regeneration in clearcuts and other disturbed areas. On good coastal  sites, they grow as tall or taller than Douglas-fir, western hemlock, and  Sitka. spruce seedlings during the first 5 years (6,51). The redcedars are  subsequently overtaken by Douglas-fir (by age 10) and western hemlock (by  age 15).

Each mature strobilus usually  produces only 3 to 6 seeds (8), but the strobili are often numerous and  heavy seed crops are common. In dry years, conebearing stands in the  interior tend to be on high, moist sites (14). Average annual seed crops  vary from 247,000 to 2,470,000 seeds per hectare (100,000 to 1  million/acre) in coastal forests and from 54,000 to 274,000/ha (22,000 to  111,000/acre) in the interior. Major seedfall occurs during October and  November in both ranges (2). Gibberellin-treated, containerized seed  orchards should permit efficient management of seed production and  harvesting (8).

    Seeds are small- 448,000 to 1,305,000/kg (203,000 to 592,000/1b) (47).  They fall faster and do not fly as far as the seeds of western hemlock,  Sitka spruce, and Douglas-fir, but dissemination is adequate within 100 m  (330 ft) of a seed source (4,30). The seeds usually germinate well without  stratification, and they retain their initial viability for at least 7  years when stored dry (5 to 8 percent moisture) at -18° C (0° F)  (8). Germination is epigeal.

When grown in the open, western  redcedars begin to produce strobili at 10 years of age and usually every  other year thereafter. Strobilus development can be artificially induced  at younger ages and increased in mature trees by girdling or treating with  gibberellin (8). The species is monoecious; male and female strobili are  produced on different branches of the same tree, at different heights-the  reddish male strobili on lower branches and the green female strobili   nearer the treetops and farther from the trunk (38,52). Anthesis and  pollination occur during March and April in southern stands near the  coast. They occur during May and June in coastal Alaska and interior  stands (47).

Intermediate redcedars are distinguishable  from dominants by age 5 on good sites. Codominants usually can be  differentiated from dominants by age 25. Mean annual height growth of the  dominants is 0.5 m (1.64 ft) in 40- to 60-year-old, pure, second-growth  stands on moist sites in western Washington (36). Annual radial increments  of 10 mm or even 20 mm (0.4 to 0.8 in) occur on the best moist sites in  the south coast region of British Columbia (39).

    Pure, even-aged stands can attain volumes comparable to pure Douglas-fir  stands by age 50 on high-quality upland sites in western Washington (37),  Plantations should be dense (about 2,470 trees per hectare or 1,000/acre),  and intermediate crown classes should be removed in a light thinning to  reduce side shade at about age 25 (22,36). Stands of 370 to 430 crop  trees/ha (150 to 175 crop trees/acre) at time of harvest may allow maximum  diameter growth without causing poor form (36). Maintaining a nearly  closed canopy at all times will benefit form because open-grown redcedars  tend to develop excessively large limbs and multiple tops. Faster growing  trees of acceptable quality can be grown at wide spacings if their lower  holes are pruned (50), but percentages of latewood decrease significantly  (49).

    Volumes of 379 to 825 m³/ha (5,418 to 11,782 ft³/acre) were  measured in 40- to 60-year-old pure second-growth stands on moist sites in  western Washington (36). A yield model on medium sites in British Columbia  indicates yields of 70 m³/ha (1,000 ft³/acre) at age 40, 350 m³/ha  (5,000 ft³/acre) at age 115, and 595 m³/ha (8,500 ft³/acre)  at age 270; maximum current annual increment occurs at 82 years and  maximum mean annual increment at 130 years (34).

    In Great Britain, the cumulative volume produced by normal western  redcedar stands on poor sites is 50 m³/ha (714 ft³/acre) at age  20 and 953 m³/ha (13,620 ft³/acre) at age 80. On good sites,  cumulative volume produced is 232 m³/ha (3,315 ft³/acre) at age  20 and 1839 m³/ha (26,268 ft³/acre) at age 80. The average age  of maximum mean annual increment is 72 on poor sites and 58 on good sites  in these British stands (22). At ages 20 and 50, cumulative volume  production is lower for western redcedar than for Douglas-fir and Sitka.  spruce in Great Britain, but by age 80 the redcedar volume production is  higher than that of Douglas-fir and spruce (45).

    Growth is often much slower. Suppressed redcedar trees that are 200  years old but only 7.6 cm. (3 in) in d.b.h. and 7.6 m (25 ft) tall are not  unusual. Survival for such long periods of suppression may be due to the  ability of the species to produce new root growth in full shade. It may  also be a result of frequent root grafting. Dominant trees often support  growth of the root systems and lower boles of suppressed trees (9).

Population Differences    Western redcedar seems to vary less than other northwestern conifer  species. Lack of isoenzyme variation in newly germinated seedlings from  western Oregon and eastern and western Washington indicates that redcedar  populations contain little genetic polymorphism (5). Isoenzyme variability  is also low in British Columbia (56). Leaf oil terpene composition is  similar in populations at both low and high elevations in British  Columbia, Washington, Oregon, Idaho, and Montana; but small differences  between coastal and interior populations were recently detected by  discriminant analysis of the chemical data (53). Seedlings from different  seed sources usually have remarkably similar forms and growth rates when  grown in the same environment. Inland populations are more tolerant of  frost than those from coastal populations, however (46), and plantation  trials indicate that provenances from Alaska are inferior to those from  Oregon and Idaho when grown in Poland (31). Seed orchards have been  established in Denmark, where resistance to leaf blight and frost have  been shown to be homozygously recessive (52).

    Races    Several horticultural varieties of western redcedar are grown in North  America. They include atrovirens, fastigiata, and pendula.  Haploid and triploid varieties have been studied in Germany (31).

    Hybrids    Thuja plicata x Thuja standishii hybrids are resistant  to the leaf blight caused by Didymascella thujina (52).

The following is a representative barcode sequence, the centroid of all available sequences for this species.

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 5
Specimens with Barcodes: 13
Species With Barcodes: 1

Year Assessed

• Needs updating

Assessor/s

Reviewer/s

Canada

Rounded National Status Rank: N5 - Secure

United States

Rounded National Status Rank: N5 - Secure

Rounded Global Status Rank: G5 - Secure

Reasons: Common species of northwest North America, with thousands of occurrences.

Please consult the PLANTS Web site and your State Department of Natural Resources for this plant’s current status, such as, state noxious status and wetland indicator values.

More info for the terms: density, natural, tree

Insects and disease:  Western redcedar is a host for several
economically important insect species.  One of the most important is the
gall midge (Mayetiola thujae), which sometimes seriously damages western
redcedar seeds in Oregon, Washington, and British Columbia [50].
Seedlings are occasionally damaged by weevils (Steremnius carenatus) in
British Columbia, and large trees are killed by bark beetles
(Phloeosinus sequoiae) on poor sites in southeastern Alaska.  The
western redcedar borer (Trachykele blondeli) causes degradation
resulting in cull of sawtimber [50].

More than 200 fungi are found on western redcedar.  A leaf blight
(Didymascella thujina) infects second- and third-year nursery seedlings.
As much as 97 percent of the natural western redcedar regeneration may
be killed when this blight reaches epidemic proportions.  The most
important fungi attacking western redcedar are root butt and trunk rots.
Poria asiatiaa and P. albipellucida are the most important trunk rots
near the coast; P. asiatioa and Phellinus weiri are the most important
in the interior range.  Rots are most evident in old stands [50].

Animal damage:  Seedlings and saplings are often severely browsed by
deer, elk, and rodents.  Browse damage may be one of the most important
stand establishment problems [50].  Grazing by cattle in burned stands
in the western redcedar/queencup beadlily (Clintonia uniflora) habitat
type in southwestern Montana retards establishment of western redcedar
[36].

Other damaging agents:  Western redcedar is often windthrown in wet
environments, but it is windfirm on dry sites [50,51].  Western redcedar
is damaged by salt spray [50].  It is also sensitive to atmospheric
pollution.  Clay dust from a brick works in British Columbia produced a
columnar form in nearby western redcedars [51].

Silvicultural considerations:  Care must be exercised when logging sites
dominated by western redcedar due to the high water table.  Bottomland
sites should not be disturbed other than to salvage high-value trees or
to remove high-risk trees.  If harvested some dead and down logs should
be left to serve as a seedbed for western redcedar and western hemlock
regeneration.  Extensive disturbance of these sites could cause
irreparable damage [13].

Western redcedar should be grown in pure stands when saw-timber,
shingles, or shakes are the desired products.  Even-aged mixtures of
western redcedar and other conifers will be harvested either too early
for the western redcedar sawtimber or too late for the other conifers
when mixed-species, even-aged stands are clearcut.  Western redcedar can
be grown in mixed stands when poles are to be produced under even-aged
management regimes.  A nearly closed canopy should be maintained at all
times.  Open-grown western redcedar tend to develop poor form, excessive
limbs, and multiple tops [51].  Western redcedar is perhaps the most
valuable species for which uneven-aged systems are applicable in the
highly productive western redcedar and western hemlock habitat types of
the Inland West [26].

Response to release:  Because western redcedar is shade tolerant, it
should be treated to minimize shock from release through slow or timely
thinning treatments.  Western redcedar's ability to respond to release
varies with tree, stand, and site conditions.  An 80-year-old western
redcedar stand, with the overstory removed and thinned, responded with
increased growth rates up to 5 years after treatment.  However, 5 to 10
years after release, growth rates slowed, and root diseases became
apparent [26].  Releasing western redcedar saplings slowly over a 17
year period had good results.  The saplings responded favorably to
release with increased growth rates and a gradual increase in vigor.
Thinning western redcedar stands should occur prior to age 30.  Spacing
of 1 foot by 1 foot (0.3 by 0.3 m) is appropriate for most young stands.
This density provides good tree and stand development and retains the
options for future intermediate treatments [25,26].

These species are introduced in Switzerland.

These plant materials are readily available from commercial sources. Contact your local Natural Resources Conservation Service (formerly Soil Conservation Service) office for more information. Look in the phone book under ”United States Government.” The Natural Resources Conservation Service will be listed under the subheading “Department of Agriculture.”

In mixed-species and uneven-aged stands, western red cedars tolerate shady understory conditions and can maintain slow but acceptable growth rates over long periods. In timber harvest of these mixed-species stands, most of these trees are taken by clearcutting. Because of steep terrain, decay, and breakage, harvesting costs are high and lumber recovery is low. Because of its high susceptibility to windthrow in wet environments and in the moist sites where growth and yield are highest, western red cedars should not be left as scattered seed trees. Even those along clearcut margins may be lost to wind throw or exposure.

Severe browse damage to western red-cedar seedlings and saplings by deer, elk, and rodents may be the most important problem in the establishment of young stands. In near-coastal sites, western red-cedar is more severely damaged by fire than any of its associates.

Shingles and shakes constitute the most important special use of  redcedar. Attractive appearance, durability, lightness, and superior  insulation qualities probably are responsible for its popularity as a  roofing material. Wood is also used in utility poles, fenceposts, piling,  paper pulp, clothes closets and chests, caskets, crates, boxes, beehives,  and fishtrap floats. Perfumes, insecticides, medicinal preparations,  veterinary soaps, shoe polishes, and deodorants are made from cedar leaf  oil. Redcedar extractives and residues are used in lead refining,  boiler-water additives, and glue extenders (31). When properly trimmed,  redcedars make excellent hedges. Their drooping branches, thin fibrous  bark, and flat sprays of scalelike leaves make redcedars attractive  ornamental trees. The leaves are a major winter food for big game in the  northern Rocky Mountains, and deer browse redcedar all year along the  coast.

Industry: The wood of western red cedar is primarily used in roofing for shingles and shakes, because of its attractive appearance, durability, lightness, and superior insulation qualities. It is also used in exterior finishings, utility poles, fence posts, piling, paper pulp, and various types of containers. The species is managed for timber in Europe and New Zealand. Cedar leaf oil is often the basis for production of perfumes, insecticides, medicinal preparations, veterinary soaps, shoe polishes, and deodorants.

Wildlife: The leaves of western red cedar are a major winter food for big game in the northern Rocky Mountains, and deer browse it all year along the coast. Many cultivars are grown for ornament, including those used for hedges. It is the provincial tree of British Columbia.

Ethnobotanic: Western red cedar has been called “the cornerstone of northwest coast Indian culture” and the large-scale use of its wood and bark delineates the cultural boundary of the northwest coast peoples within its range. Wood served for house planks, house posts, roof boards, various kinds of boxes, and canoes. It is easy to split and was often used for bentwood boxes. Bark was made into skirts, capes, and complete dresses for women, and roots and limbs were used for baskets and rope. The inner bark was used for slow matches to carry the fire from camp to camp, and also as mats, and baskets. Various medicines were derived from the tree.