dcsimg

Comments

provided by eFloras
Isolated stands of Thuja occidentalis occur north and east of its general range in Canada (to 51° 31' N latitude in Ontario, 50° N in Quebec). In the United States south of the Great Lakes and in southern New England, it occurs locally in scattered stands and is rare or extirpated at numerous former sites. In some areas, heavy winter browsing by deer greatly reduces reproductive success through elimination of seedlings or saplings.

Thuja occidentalis is widely utilized in ornamental silviculture and has more than 120 named cultivars. It was probably the first North American tree introduced into Europe (ca. 1566). It is an important timber tree; the wood is used for applications requiring decay resistance.

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Missouri Botanical Garden, 4344 Shaw Boulevard, St. Louis, MO, 63110 USA
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Flora of North America Vol. 2 in eFloras.org, Missouri Botanical Garden. Accessed Nov 12, 2008.
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Flora of North America Editorial Committee
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Comments

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Planted for timber.
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Missouri Botanical Garden, 4344 Shaw Boulevard, St. Louis, MO, 63110 USA
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Flora of China Vol. 4: 64 in eFloras.org, Missouri Botanical Garden. Accessed Nov 12, 2008.
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Flora of China @ eFloras.org
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Wu Zhengyi, Peter H. Raven & Hong Deyuan
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Description

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Trees to 15(--38) m, stunted or prostrate in harsh environments; trunk to 0.9(--1.8) m diam., sometimes divided into 2--3 secondary stems, often reproducing by layering or forming erect, rooted branches from fallen trunks; crown conical. Bark reddish brown or grayish brown, 6--9 mm thick, fibrous, fissured. Leaves of branchlets (1.5--)3--5 mm, acute, dull yellowish green on both surfaces of branchlets. Pollen cones 1--2 mm, reddish. Seed cones ellipsoid, (6--)9--14 mm, brown; fertile scales usually 2 pairs, each minutely mucronate. Seeds ca. 8 per cone, 4--7 mm (including wings), reddish brown. 2 n = 22.
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Missouri Botanical Garden, 4344 Shaw Boulevard, St. Louis, MO, 63110 USA
bibliographic citation
Flora of North America Vol. 2 in eFloras.org, Missouri Botanical Garden. Accessed Nov 12, 2008.
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Flora of North America @ eFloras.org
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Flora of North America Editorial Committee
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Description

provided by eFloras
Trees to 15(-38) m tall; trunk 0.9(-1.8) m d.b.h.; bark reddish brown or grayish brown, fibrous, fissured; crown conical. Leaves on both sides of branchlets dull yellowish-green; facial leaves (1.5-)3-5 mm, abaxial gland conspicuous, apex acute; lateral leaves slightly shorter than or as long as facial leaves, apex incurved. Pollen cones reddish, 1-2 mm. Seed cones brown, ellipsoid, (0.6-)0.9-1.4 cm; fertile cone scales ca. 4. Seeds reddish-brown, 4-7 mm including wings.
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copyright
Missouri Botanical Garden, 4344 Shaw Boulevard, St. Louis, MO, 63110 USA
bibliographic citation
Flora of China Vol. 4: 64 in eFloras.org, Missouri Botanical Garden. Accessed Nov 12, 2008.
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Flora of China @ eFloras.org
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Wu Zhengyi, Peter H. Raven & Hong Deyuan
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eFloras.org
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Distribution

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Man., N.B., N.S., Ont., P.E.I., Que.; Conn., Ill., Ind., Ky., Maine, Md., Mass., Mich., Minn., N.H., N.Y., N.C., Ohio, Pa., Tenn., Vt., Va., W.Va., Wis.
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copyright
Missouri Botanical Garden, 4344 Shaw Boulevard, St. Louis, MO, 63110 USA
bibliographic citation
Flora of North America Vol. 2 in eFloras.org, Missouri Botanical Garden. Accessed Nov 12, 2008.
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Flora of North America @ eFloras.org
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Flora of North America Editorial Committee
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Habitat

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On mostly calcareous substrates, neutral to basic swamps, shores of lakes and rivers, uplands, cliffs, and talus; 0--900m.
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Missouri Botanical Garden, 4344 Shaw Boulevard, St. Louis, MO, 63110 USA
bibliographic citation
Flora of North America Vol. 2 in eFloras.org, Missouri Botanical Garden. Accessed Nov 12, 2008.
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Flora of North America @ eFloras.org
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Flora of North America Editorial Committee
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Habitat & Distribution

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Planted for timber. Anhui, Guizhou, Hebei, Henan, Hubei, Jiangsu, Jiangxi, Shandong, Sichuan, Zhejiang [native to E Canada, NE United States].
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Missouri Botanical Garden, 4344 Shaw Boulevard, St. Louis, MO, 63110 USA
bibliographic citation
Flora of China Vol. 4: 64 in eFloras.org, Missouri Botanical Garden. Accessed Nov 12, 2008.
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Flora of China @ eFloras.org
editor
Wu Zhengyi, Peter H. Raven & Hong Deyuan
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Synonym

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Thuja obtusa Moench; T. theophrasti C. Bauhin ex Nieuwland.
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Missouri Botanical Garden, 4344 Shaw Boulevard, St. Louis, MO, 63110 USA
bibliographic citation
Flora of China Vol. 4: 64 in eFloras.org, Missouri Botanical Garden. Accessed Nov 12, 2008.
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Flora of China @ eFloras.org
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Wu Zhengyi, Peter H. Raven & Hong Deyuan
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Common Names

provided by Fire Effects Information System Plants
northern white-cedar
northern whitecedar
white-cedar
white cedar
eastern white-cedar
eastern arborvitae
arborvitae
arbor vitae
swamp-cedar
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bibliographic citation
Carey, Jennifer H. 1993. Thuja occidentalis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Cover Value

provided by Fire Effects Information System Plants
More info for the term: cover

Stands of northern white-cedar provide thermal cover for white-tailed
deer, moose, and black bear [4,9,39].
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bibliographic citation
Carey, Jennifer H. 1993. Thuja occidentalis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Description

provided by Fire Effects Information System Plants
More info for the terms: monoecious, tree

Northern white-cedar is a monoecious, native, evergreen tree with a
narrow, almost columnar crown. Branches on open-grown trees extend to
the ground. The trunk is often divided into two or more secondary
trunks of equal size. Northern white-cedar has scalelike foliage and
fibrous, sometimes shredding bark [25,26].

At maturity northern white-cedar is 40 to 50 feet (12-15 m) tall and 12
to 24 inches (30-60 cm) in d.b.h. Infrequently it reaches heights of 70
to 80 feet (21-24 m) and diameters of 48 to 60 inches (120-150 cm) [26].
This species is extremely slow growing; after 50 years, it might reach
40 feet (12 m) in height on good sites, but only 15 feet (4.6 m) or less
on poor sites [27].

Northern white-cedar reaches ages in excess of 800 years [5,32]. Two
trees on the Niagara Escarpment in southern Ontario were dated at 935
and 1,032 years [32].

Seedlings develop deep roots in well-drained soil and shallow roots in
saturated soil. With age, northern white-cedar develops a widespreading
root system which is well adapted to secure water and nutrients from
cracks in rocks [26].
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bibliographic citation
Carey, Jennifer H. 1993. Thuja occidentalis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Distribution

provided by Fire Effects Information System Plants
Northern white-cedar occurs in southeastern Canada and the adjacent
northern United States. It is distributed from southwestern Nova
Scotia, Prince Edward Island, New Brunswick, the Gaspe Peninsula in
Quebec, and Anticosti Island in the Gulf of Saint Lawrence; west to
northern Ontario and southeastern Manitoba; south to southeastern
Minnesota and northern Illinois; and east through extreme northwestern
Indiana, Michigan, and the New England states. Island populations occur
in the Appalachian Mountains in western Pennsylvania, West Virginia,
Virginia, and eastern Tennessee. Local populations also occur in
west-central Manitoba, Wisconsin, Minnesota, Illinois, and Ohio [26,33].
Historical evidence indicates that northern white-cedar is native to
North Carolina as well, but no known native population occurs there now
[10].
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bibliographic citation
Carey, Jennifer H. 1993. Thuja occidentalis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Fire Ecology

provided by Fire Effects Information System Plants
More info for the terms: cover, crown fire, density, fire regime, forest, fuel, organic soils, peat, seed

Northern white cedar is highly susceptible to fire because of thin bark,
shallow roots, and high oil content [26]. In the understory of a pine,
aspen, or birch (Betula spp.) forest, northern white-cedar acts as a fuel
ladder, carrying fire into the overstory [23].

The risk of fire on most northern white-cedar sites is low, but fires
occasionally originate on drier sites and spread into northern
white-cedar stands [34]. Forested peatlands with a moss ground cover
will not carry spring fires because of a high water table, but forested
fens with a ground cover of sedges (Carex spp.) and grasses carry fire
in the spring when the grasses and sedges are dry. Most fires in
peatlands with a moss ground cover occur in July, August, or September.
Given sufficient winds, northern white-cedar stands can carry a crown
fire [22].

Northern white-cedar reproduces well on moist organic soils exposed by
fire if a seed source is nearby. Many northern white-cedar forests in
the Lake States originated after fire [14]. However, if the peat burns
and the humus is destroyed, northern white-cedar may not become
established for a long time [34].

Vogl [47] classifies northern white-cedar as a fire-initiated species in
which fire simultaneously terminates and initiates a long-lived species.
Fires are infrequent and usually severe. The longest lived specimens
occur in locations where fire is infrequent or nonexistent because of
rocky substrate, sparse ground cover, or low stand density [5].
Examples of such sites include the lakeshores and islands of Lake
Duparquet, Quebec [6] and the Niagara Escarpment in Ontario [32].
Recurring fire may be responsible for the exclusion of northern
white-cedar from some sites [6].

FIRE REGIMES :
Find fire regime information for the plant communities in which this
species may occur by entering the species name in the FEIS home page under
"Find FIRE REGIMES".
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cc-publicdomain
bibliographic citation
Carey, Jennifer H. 1993. Thuja occidentalis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Fire Management Considerations

provided by Fire Effects Information System Plants
More info for the terms: cover, prescribed fire

Prescribed fire is recommended after northern white-cedar harvest unless
there is ample advance regeneration or if the organic soil is
unsaturated. Fire removes the heavy slash that prevents regeneration
and also prepares a favorable seedbed [27,46]. However, deep ground
fires can start if the soil is not saturated [27].

If removing slash is the primary objective, prescribed fires are usually
conducted under the following conditions: 3 to 10 days after a rainfall
of more than 0.1 inch (0.3 cm), a minimum relative humidity of 30 to 60
percent, a maximum air temperature of 60 to 90 degrees Fahrenheit (16-32
deg C), and a maximum wind speed of 5 to 15 miles per hour (8-24 km/h).
If the objective is to remove slash and prepare a seedbed, the fire must
be hotter and is usually conducted under the following conditions: at
least 7 days since a rainfall of more than 0.1 inch (0.3 cm), less than
45 percent relative humidity, air temperatures greater than or equal to
80 degrees Fahrenheit (27 deg C), and 5 to 15 miles per hour (8-24 km/h)
wind speed [27].

The effect of three different slash treatments on northern white-cedar
regeneration after winter clearcutting was investigated. The treatments
were (1) a prescribed broadcast fire in August to burn the slash, (2)
skidding entire trees out of the study area and delimbing elsewhere, and
(3) leaving the slash in place. Five growing seasons after
clearcutting, northern white-cedar less than or equal to 23.6 inches (60
cm) tall averaged 33.3 stems per miliacre (8.2 stems/sq m) on burned
plots, and 11.5 and 22.2 stems per miliacre (2.8 and 5.5 stems/sq m) on
full-tree skidded and slash-left plots, respectively. Ten growing
seasons after clearcutting, northern white-cedar had increased to 40.2
stems per miliacre (9.9 stems/sq m) on burned plots but showed no change
on the other treatment plots [46].

Northern white-cedar slash is a fire hazard for 20 to 30 years because
of its resistance to decay [42].

Prescribed fire can be used to eliminate northern white-cedar that
invades fens in the absence of fire. A low intensity fall fire (rarely
exceeding 70 BTU/sec/sq ft) resulted in a statistically significant
reduction in the percent cover of northern white-cedar for three
postfire growing seasons. Annual prescribed burning is recommended for
restoring fens [40,41].
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bibliographic citation
Carey, Jennifer H. 1993. Thuja occidentalis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Growth Form (according to Raunkiær Life-form classification)

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More info on this topic.

More info for the term: phanerophyte

Phanerophyte
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bibliographic citation
Carey, Jennifer H. 1993. Thuja occidentalis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Habitat characteristics

provided by Fire Effects Information System Plants
More info for the terms: association, bog, ecotype, litter, minerotrophic, peat, seed, shrub, swamp, tree

Northern white-cedar grows on both uplands and lowlands. The uplands
are primarily seepage areas, old fields, and limestone cliffs and
boulder fields. The lowland sites include swamps, streambanks, and
lakeshores. Northern white-cedar occurs from near sea level to more
than 2,000 feet (600 m) in elevation. It grows up to 4,270 feet (1,300
m) in the Adirondack Mountains in New York on sites where water is
flowing over rocks [26].

On lowland sites, northern white-cedar generally grows where there is a
strong flow of moderately mineral-rich soil water of near neutral pH
(minerotrophic and weakly minerotrophic swamps) and where the organic
peat is moderately to well decomposed. The peat is usually 1 to 6 feet
(0.3-1.8 m) thick and contains rotten wood. Northern white-cedar grows
best where soils are neutral to moderately alkaline [19,24,26].

On upland sites, northern white-cedar grows primarily in calcareous
soils including calcareous clays and shallow loam overlying broken
limestone [26].

Habeck [50] has suggested that northern white-cedar growing in limestone
uplands is an ecotype distinct from wet lowland northern white-cedar.
Specimens growing on cliffs tend to be deformed with multiple leaders
and twisted trunks, whereas those in wet lowlands tend to be more erect
with well-defined trunks. However, four studies that looked at tree
morphology [8], seed morphology [7], growth patterns [36], and xylem
water potential [12] found no evidence of ecotypic variation. There
tended to be more variation within a single site than between lowland
and upland sites. Seedlings, from seeds collected from the two
contrasting habitats, were grown under different moisture conditions.
Xerically grown seedlings had significantly (p less than 0.05) more negative xylem
water potential than did seedlings grown under moist conditions,
independent of seed origin. The seedlings acclimated to the conditions
and demonstrated that northern white-cedar has broad physiological
tolerance to habitat moisture [12].

Overstory associates not mentioned in DISTRIBUTION AND OCCURRENCE
include white spruce (Picea glauca), quaking aspen (Populus
tremuloides), balsam poplar (P. balsamifera), and bigtooth aspen. Shrub
associates on good sites include speckled alder, mountain maple (Acer
spicatum), red-osier dogwood (Cornus stolonifera), and American fly
honeysuckle (Lonicera canadensis). Bog Labrador-tea (Ledum
groenlandicum), blueberries (Vaccinium spp.), and wintergreen
(Gaultheria procumbens) occur on poorer sites. Creeping wintergreen (G.
hispidula) occurs on both good and poor sites [26].

Herbs that occur in swamps with northern white-cedar include dwarf red
blackberry (Rubus pubescens), Canada mayflower (Maianthemum canadense),
woodfern (Dryopteris spp.), bunchberry dogwood (Cornus canadensis),
false Solomons-seal (Smilacina spp.), and pitcherplant (Sarracenia
purpurea) [26]. Dwarf lake iris (Iris lacustris), a federally threatened
species endemic to the northern shores of Lake Michigan and Lake Huron,
is found in association with narrow beach strands of northern
white-cedar [43].

The groundcover in northern white-cedar swamp forests includes sphagnum
and other mosses, liverworts, decaying logs, and litter [26].
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bibliographic citation
Carey, Jennifer H. 1993. Thuja occidentalis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Habitat: Cover Types

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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):

5 Balsam fir
12 Black spruce
13 Black spruce - tamarack
21 Eastern white pine
23 Eastern hemlock
24 Hemlock - yellow birch
30 Red spruce - yellow birch
32 Red spruce
33 Red spruce - balsam fir
35 Paper birch - red spruce - balsam fir
37 Northern white-cedar
38 Tamarack
39 Black ash - American elm - red maple
108 Red maple
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Carey, Jennifer H. 1993. Thuja occidentalis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Habitat: Ecosystem

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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):

FRES10 White - red - jack pine
FRES11 Spruce - fir
FRES17 Elm - ash - cottonwood
FRES18 Maple - beech - birch
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bibliographic citation
Carey, Jennifer H. 1993. Thuja occidentalis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Habitat: Plant Associations

provided by Fire Effects Information System Plants
More info on this topic.

This species is known to occur in association with the following plant community types (as classified by Küchler 1964):

More info for the terms: bog, forest

K093 Great Lakes spruce - fir forest
K094 Conifer bog
K095 Great Lakes pine forest
K096 Northeastern spruce - fir forest
K101 Elm - ash forest
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bibliographic citation
Carey, Jennifer H. 1993. Thuja occidentalis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Immediate Effect of Fire

provided by Fire Effects Information System Plants
More info for the terms: cover, surface fire

Northern white-cedar is usually killed by surface fire. Large trees may
survive if ground cover is sparse.
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bibliographic citation
Carey, Jennifer H. 1993. Thuja occidentalis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Importance to Livestock and Wildlife

provided by Fire Effects Information System Plants
Northern white-cedar provides food and shelter for wildlife.
White-tailed deer, snowshoe hares, and porcupines heavily browse the
foliage [26]. Northern white-cedar is one of the best winter browse
species for white-tailed deer in the northern Lake States, and it is
often overbrowsed [2]. Moose browse northern white-cedar only when
other food is scarce. In a study on Isle Royale in Michigan, northern
white-cedar constituted only 0.7 percent of the moose diet, but 5.8
percent of the available food [3].

Pileated woodpeckers feed on carpenter ants that, in turn, nest in and
feed on the heartwood of northern white-cedar [13]. Other birds that
are especially abundant in northern white-cedar forests include
white-throated sparrows, golden-crowned kinglets, yellow-bellied
flycatchers, ovenbirds, northern parulas, winter wrens, Swainson's
thrushes, and numerous warblers. Blackburnian warblers, Cape May
warblers, ovenbirds, and golden-crowned kinglets breed in the densest
stands [18].
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bibliographic citation
Carey, Jennifer H. 1993. Thuja occidentalis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Key Plant Community Associations

provided by Fire Effects Information System Plants
More info for the terms: bog, fen, forest, hardwood, swamp

Northern white-cedar is an important species in the wet-mesic coniferous
forests of the northern lowlands [14]. It is often present in the
ecotone between sphagnum bog and upland hardwood communities [15]. It
may dominate rich swamp forests, poor swamp forests, and the cedar
string bog and fen complex [24].

The following published classifications list northern white-cedar as
dominant or codominant:

The vegetation of Wisconsin [14]
Virgin plant communities of the Boundary Waters Canoe Area [37]
Plant communities of Voyageurs National Park, Minnesota, U.S.A. [30]
Habitat classification system for Upper Peninsula of Michigan and
northeast Wisconsin [11]
Classification and gradient analysis of forest vegetation of Cape
Enrage, Bic Park, Quebec [49]
The principal plant associations of the Saint Lawrence Valley [16]
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Carey, Jennifer H. 1993. Thuja occidentalis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Life Form

provided by Fire Effects Information System Plants
More info for the term: tree

Tree
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bibliographic citation
Carey, Jennifer H. 1993. Thuja occidentalis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Management considerations

provided by Fire Effects Information System Plants
More info for the terms: competition, forest, prescribed fire, tree

There is interest in regenerating northern white-cedar after harvest
because of its forage value to white-tailed deer and because of the
popularity of northern white-cedar log cabins. In the past, forest
managers have not successfully regenerated this species. Northern
white-cedar is a slow-growing species, and seedlings are frequently
damaged by heavy browsing. Many former northern white-cedar stands are
now dominated by balsam fir (Abies balsamea), spruce (Picea spp.), aspen
(Populus spp.), or speckled alder (Alnus rugosa) [31].

A combination of clearcut and shelterwood strips is currently
recommended for harvesting mature stands of northern white-cedar and
reproducing new ones, although other possible methods should be
investigated [27]. If there are less than 10 northern white-cedar
advance regeneration stems per miliacre (2.5 stems/sq m), a prescribed
fire after clearcutting is recommended to eliminate heavy slash, set
back competition, and prepare a seedbed [27,31,46]. See FIRE EFFECTS for
further details on the influence of fire on regeneration.

Sapling stands provide the most browse for deer [26]. Overbrowsing can
retard the growth and even kill a tree if it is less than 7 feet (2.1 m)
tall [2]. A high browse line is frequently evident on larger trees [9].
Fifteen to twenty percent annual usage of foliage might maintain a
constant food supply and still permit a suitable growth rate for
saplings [2]. Thinning of stands improves deer habitat and timber
quality [18].

Northern white-cedar is relatively free of serious insect injury. The
principal pests are arborvitae leafminer (Argyresthia thuiella) and
black and red carpenter ants (Camponotus pennsylvanicus and C.
ferrugineus). Northern white-cedar is affected by few serious diseases
[26].

Higher than normal water levels will reduce growth and eventually kill
trees. Beaver damming and road construction are often responsible for
impeded drainage [26,27].
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bibliographic citation
Carey, Jennifer H. 1993. Thuja occidentalis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Nutritional Value

provided by Fire Effects Information System Plants
Northern white-cedar browse is, on average by wet weight, 2.7 percent
protein, 5.2 percent fat, 27.5 percent carbohydrates, and 13.9 percent
crude fiber [44]. It is high in calcium [29]. The browse is considered
highly nutritious [2] and is more digestible to white-tailed deer than
bigtooth aspen (Populus grandidentata) browse [44].
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bibliographic citation
Carey, Jennifer H. 1993. Thuja occidentalis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Occurrence in North America

provided by Fire Effects Information System Plants
CT HI IL IN ME MD MA MI MN NH
NY OH PA RI TN VT VA WV WI MB
NB NS ON PE PQ
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Carey, Jennifer H. 1993. Thuja occidentalis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Other uses and values

provided by Fire Effects Information System Plants
Northern white-cedar is widely planted as an ornamental. Northern
white-cedar leaf oil is distilled from boughs and used for perfume and
medicines. The foliage is rich in vitamin C; Native Americans and early
European explorers used it to treat scurvy [26].

Because of its long life span, northern white-cedar is a valuable
species for dendroclimatic research [5].
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bibliographic citation
Carey, Jennifer H. 1993. Thuja occidentalis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Palatability

provided by Fire Effects Information System Plants
Northern white-cedar browse is highly palatable to white-tailed deer
[2].
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Carey, Jennifer H. 1993. Thuja occidentalis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Phenology

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Flower buds form in autumn and expand the following spring. Pollen is
dispersed from late April to June. Cones are full grown by mid-August,
ripen in August and September, and open 7 to 10 days after ripening.
Seeds germinate the following spring or early summer when sufficiently
high temperatures occur [26].
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Carey, Jennifer H. 1993. Thuja occidentalis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Plant Response to Fire

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More info for the terms: competition, seed

Northern white-cedar becomes established by seed on recently burned
sites if a seed source is nearby and the exposed soil is moist
[14,34,47]. Fire serves to remove competition and also removes the moss
layer that dries out in the summer and results in seedling mortality
[31].
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Carey, Jennifer H. 1993. Thuja occidentalis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Post-fire Regeneration

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More info for the terms: root crown, secondary colonizer

Tree without adventitious-bud root crown
Secondary colonizer - off-site seed
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Carey, Jennifer H. 1993. Thuja occidentalis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Regeneration Processes

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More info for the terms: adventitious, layering, organic soils, swamp, tree

Sexual reproduction: Northern white-cedar begins producing cones as
young as 6 years of age and begins producing large quantities by age 30.
The best production occurs after age 75. Good crops occur at 2- to
5-year intervals with intervening years having fair to medium crops.
Seeds have lateral wings and are disseminated by wind. Seeds are
dispersed a distance of 150 to 200 feet (45-60 m) from the source tree
[13,14,26].

Germination occurs when daytime temperatures reach about 84 degrees
Fahrenheit (29 deg C) [21]. Northern white-cedar germinates on a
variety of substrates including both mineral and organic soils, but
seedling establishment is limited to sites with a constant moisture
supply [26]. Drought is a major cause of seedling mortality [14].
Seedlings that germinate on old stumps are likely to die when the stumps
dry out in late summer, and seedlings that germinate in fast-growing
sphagnum moss (Sphagnum spp.) may be smothered [13]. Seedlings prosper
on recently burned sites [26].

Seedling growth is slow. Annual height growth averages 3 inches (8 cm)
in the first few years. Partial light is needed for continued seedling
growth [26].

Vegetative reproduction: Under favorable moisture conditions, northern
white-cedar reproduces vegetatively by layering. Seedlings may
reproduce by layering at age 5 or earlier. Layering accounts for a
considerable amount of northern white-cedar reproduction. It is common
in swamp forests where trees often fall or tip slowly. Trees
established on logs and stumps may fall as their weight increases and
the substrate rots [13,14,26].

Branches on a fallen tree that still has functional roots may begin
growing vertically. Eventually, with the increased weight of new
growth, the stem will contact the soil and put out adventitious roots
[13].
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Carey, Jennifer H. 1993. Thuja occidentalis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Successional Status

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More info for the terms: climax, seed, succession, swamp, tree

Although northern white-cedar is generally considered shade tolerant, it
is not as tolerant as balsam fir or sugar maple (Acer saccharum).
Seedlings may only be intermediate in shade tolerance [13,26]. They can
survive severe suppression for several years, but if not released, they
die [26]. Vegetative shoots are more tolerant than seedlings. Although
some authors [6,30,31] consider northern white-cedar a climax species
because of its longevity and shade tolerance, it cannot reproduce by
seed under dense shade to any marked extent [13].

Northern white-cedar will invade and form even-aged stands in old
fields, openings created by windfall or cutting, and recently burned
swamp sites. It replaces speckled alder thickets that form in swamps
after fire or after changes in water levels [19,26]. Northern
white-cedar is a pioneer on limestone cliffs and talus slopes. The
roots grow in small pockets of organic material between rocks [49].
Northern white-cedar succeeds less tolerant, shorter lived species such
as balsam poplar, tamarack (Larix laricina), and black spruce (Picea
mariana) [26].

An uneven-aged old-growth northern white-cedar community occurs on the
Niagara Escarpment in southern Ontario. This self-sustaining population
occurs in a 3.3 to 16.4-foot (1-5 m) wide strip on the limestone cliff
edge and face [32]. Uneven-aged stands also form on poor lowland sites
where vegetative reproduction is the primary mode of reproduction [26].

Northern white cedar is often succeeded by sugar maple and other more
shade-tolerant species [1,17]. Replacement is usually tree by tree, but
major disturbance (excluding fire) can accelerate succession by
releasing shade-tolerant species [balsam fir, sugar maple, black ash
(Fraxinus nigra)] growing in the understory [1,19].
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Carey, Jennifer H. 1993. Thuja occidentalis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Taxonomy

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The currently accepted scientific name for northern white-cedar is Thuja
occidentalis L. [33].
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Carey, Jennifer H. 1993. Thuja occidentalis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Wood Products Value

provided by Fire Effects Information System Plants
The wood of northern white-cedar is resistant to decay. It is used for
products that come in contact with water and soil, such as fence posts,
shingles, paneling, and boats [25,26]. Northern white-cedar logs are
especially popular to use for log cabins because the wood has good
insulating qualities [31]. It is also used for kraft pulp and particle
board [26].
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Carey, Jennifer H. 1993. Thuja occidentalis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Associated Forest Cover

provided by Silvics of North America
Northern white-cedar most commonly grows in mixed stands but is also found in pure stands. It comprises a majority of the stocking or is pure in the Northern White-Cedar forest cover type (Society of American Foresters Type 37) and is an associate species in the following types (13):

    5  Balsam Fir
  12  Black Spruce
  13  Black Spruce-Tamarack
  21  Eastern White Pine
  23  Eastern Hemlock
  24  Hemlock-Yellow Birch
  30  Red Spruce-Yellow Birch
  32  Red Spruce
  33  Red Spruce-Balsam Fir
  35  Paper Birch-Red Spruce-Balsam Fir
  38  Tamarack
  39  Black Ash-American Elm-Red Maple
108  Red Maple

The northern white-cedar type commonly includes some balsam fir (Abies balsamea) and tamarack (Larix laricina) in the boreal region of Canada but tends to be mixed with additional species farther south. Balsam fir, black spruce (Picea mariana), white spruce (P. glauca), red spruce (P. rubens), tamarack, black ash (Fraxinus nigra), and red maple (Acer rubrum) are common associates on the wetter sites, especially swamps. Yellow birch (Betula alleghaniensis), paper birch (B. papyrifera), quaking aspen (Populus tremuloides), bigtooth aspen (P. grandidentata), balsam poplar (P. balsamifera), eastern hemlock (Tsuga canadensis), and eastern white pine (Pinus strobus) are common on the better drained sites, especially uplands.

Except when dense, northern white-cedar stands usually have an undergrowth of shrubs and herbs. Speckled alder (Alnus rugosa) is commonly the most important shrub on the better sites. Other characteristic shrubs on the better sites (especially in swamps) include mountain maple (Acer spicatum), red-osier dogwood (Cornus stolonifera), and fly honeysuckle (Lonicera canadensis). On poorer sites they include Labrador-tea (Ledum groenlandicum), blueberries (Vaccinium spp.), and wintergreen (teaberry) (Gaultheria procumbens); creeping snowberry (G. hispidula) is common on both kinds of sites (see 16 for a more complete list). Characteristic herbs on the better sites (especially in swamps) include dwarf raspberry (Rubus pubescens), false lily-of-the-valley (Maianthemum canadense), woodfern (Dryopteris spp.), and bunchberry (Cornus canadensis). On poorer sites they include false Solomons-seal (Smilacina trifolia) and pitcherplant (Sarracenia purpurea). Ground cover is usually a mosaic of sphagnum (Sphagnum spp.) and other mosses, liverworts, decaying logs, and litter (13).

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Climate

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Northern white-cedar grows in a relatively humid climate. Annual precipitation commonly ranges from 710 to 1170 mm (28 to 46 in), but the extremes range from about 510 mm (20 in) at the tree's northern and western limits to 1400 mm (55 in) in the southern Appalachians. One-third to one-half of the precipitation occurs during the warm season. Snowfall ranges from about 100 cm (40 in) to more than 380 cm (150 in) annually.

Temperatures are often cool during a moderately short growing season. The northern limit of the range extends to the forest-tundra transition (subarctic zone) in Canada. The southern limit has an average annual temperature of less than 10° C (50° F) in the Lake States and up to 16° C (60° F) in the southern Appalachians. Average January temperatures commonly range from -12° to -4° C (10° to 24° F) and those of July from 16° to 22° C (60° to 72° F). The average frost-free period commonly ranges from about 90 to 180 days, but the extremes range from less than 80 days at the tree's northern limit to about 200 days in the southern Appalachians (16).

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Damaging Agents

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On wet sites such as swamps, restricted soil aeration resulting from abnormally high water levels usually reduces the growth rate of northern white-cedar and may kill entire stands. Wetland road crossings and beaver damming are the primary causes of flooding. Road-caused flooding has killed white-cedar or reduced its growth on thousands of hectares in northern Minnesota (45); natural gas and petroleum pipelines will probably have similar effects unless cross drainage is provided (4).

Wind-induced uprooting and breakage sometimes occur in older stands on both upland and swamp sites, especially along exposed edges and in stands opened by partial cutting (27). Large trees and those with basal defect are most susceptible to wind damage.

Northern white-cedar is highly susceptible to fire damage because its bark is thin and has a high oil content; its shallow roots are easily damaged even by light ground fires (6). On the Laurentian Shield in northeastern Minnesota, this species has been driven to the lakeshores by fire (23). The risk of wildfire is low, however, on most white-cedar areas in the United States and good fire protection now results in little loss (27).

Snow and ice often damage northern white-cedar by breaking limbs (6); they also break stems or force trees into a permanent leaning position (7,9).

Agents that turn northern white-cedar foliage yellow or brown and sometimes cause severe damage or death include unfavorable winter weather, deicing salts, and drought. Plantings are particularly susceptible to winterkill caused by dehydration (40). The tree's tolerance of deicing salts is only moderate or intermediate (15,46); so branches exposed to salt spray along highways commonly have severe dieback. In Iowa windbreaks, white-cedar had more drought damage than other evergreens during a very dry winter (37). When the oldest foliage turns rusty red in the fall, however, it is a natural shedding of branchlets (cladoptosis) (39).

Northern white-cedar is relatively free from serious insect injury (9,39). Carpenter ants and leafminers are probably its principal insect pests. The black carpenter ant (Camponotus pennsylvanicus) commonly reduces the timber value of large trees and often makes them subject to windbreakage. The red carpenter ant (C. ferrugineus) has caused significant damage in Minnesota (2).

Leafminers are common pests of northern white-cedar. They have caused severe "scorching" of foliage and often subsequent twig, branch, or tree mortality in southeastern Canada (39). Outbreaks of the arborvitae leafminer (Argyresthia thuiella) have severely damaged white-cedar stands in Maine, and damage to ornamentals and nursery seedlings is often severe. Ornamental white-cedars are also subject to serious injury by another leafminer, Coleotechnites thujaella (2).

Several other insects and related organisms (such as mites) feed on northern white-cedar, but only a few are important. The bagworm (Thyridopteryx ephemeraeformis), juniper scale (Carulaspis juniperi), and spruce spider mite (Oligonychus ununguis) can significantly damage ornamental white-cedars (39,50). Heavy infestations of the Fletcher scale (Lecanium fletcheri), arborvitae aphid (Cinara tujafilina), and arborvitae weevil (Phyllobius intrusus) have occurred in nurseries (2).

Northern white-cedar has few serious diseases as a forest tree, especially in immature stands; whereas in cultivation it is subject to several seedling and foliage diseases. Seedlings seem to be resistant to damping-off fungi, however. The foliage-blight fungi Phomopsis juniperovora and Didymascella thujina are among the main organisms causing seedling diseases. Beyond the seedling stage Phomopsis juniperovora blights foliage and shoots under humid conditions, and Didymascella thujina causes some unsightliness. In Quebec a snow-blight fungus (Phacidium sp.) has caused important damage in nurseries and hedges (24).

Although several root- and butt-rot fungi attack northern white-cedar, they mainly attack old or damaged trees. Because fruiting bodies of these fungi seldom appear on living trees, the most common outward sign of rot is woodpecker holes. Poria subacida, causing a white stringy butt rot, and balsam (or brown) butt rot (Tyromyces balsameus) and red-brown butt rot (Phaeolus schweinitzii), both causing cubical rots, are common in trees on knolls or other drier parts of swamps (16). Balsam butt rot can also cause extensive root rot in suppressed white-cedars (24).

Winter browsing by white-tailed deer often severely damages older seedling- and sapling-stage northern white-cedar in the Lake States and can prevent the satisfactory reestablishment of the type after harvesting (27), especially in deeryards. In some areas, however, damage from snowshoe hares is as great as, or greater than, from deer (16).

Porcupines sometimes kill white-cedar trees or lower their growth and timber quality by feeding heavily on foliage and by girdling stems and branches. Red squirrels frequently clip branchlets with flower buds and cone clusters, and thus may significantly reduce the supply of seed available for reproduction (6). Both porcupine and squirrel damage contribute to the prevalence of stag-headedness in old trees (9).

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Flowering and Fruiting

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Male and female flowers of northern white-cedar, a monoecious species, are usually borne on separate twigs or branchlets; they are tiny, terminal, cone-like bodies. Male flowers are yellowish and arise from branchlets near the base of the shoot; female flowers are pinkish and appear at the tips of short terminal branchlets. Ripe cones are pale cinnamon brown, oblong, and 8 to 13 mm (0.3 to 0.5 in) long.

In northeastern Minnesota, flower buds, which form during autumn, begin to expand the following spring from about mid-April to early May; pollen dispersal begins from late April to early June (1). In northern Michigan flowering occurs from late April to early May, pollinated conelets begin to grow rapidly in late June, cones are full grown by mid-August, and cones ripen from August to September (16,34,41). The period between cone ripening and cone opening is only from 7 to 10 days.

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Genetics

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Population Differences and Races Northern white-cedar is morphologically similar throughout its range, with no races or varieties reported. But a rangewide provenance study indicates that significant genetic variation does exist.

In the Lake States, provenances from intermediate latitudes generally grew best (26); in Illinois, provenances from south of the species' main range were shortest but a definite geographic pattern was lacking, perhaps because of localized ecotypes (29). In Wisconsin, upland and lowland populations less than 0.7 km (0.4 mi) apart may form separate ecotypes (33), but the extent of differentiation seems to vary from one area to another.

The existence of more than 120 ornamental cultivars of northern white-cedar, which differ in foliage color and growth habit, also reflects significant genetic variation in natural populations.

Hybrids No natural or artificial hybrids have been reported (6,33).

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Growth and Yield

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Northern white-cedar is a medium-sized tree, commonly 12 to 15 m (40 to 50 ft) tall and 30 to 60 cm (12 to 24 in) in d.b.h. at maturity. Infrequently it reaches 21 to 24 m (70 to 80 ft) tall and 120 to 150 cm (48 to 60 in) in d.b.h. (10). Maximum dimensions reported are more than 30 m (100 ft) in height and 180 cm (72 in) in d.b.h. White-cedar reaches a maximum age of 400 years or more in swamps or on other lowland sites (16).

The growth rate of northern white-cedar is greatly affected by site productivity and is expressed as site index or the height of dominants at age 50 years. In the Lake States, site index ranges from about 12 m (40 ft) on the best sites to 5 m (15 ft) on the poorest (27). Indications are that the site productivity of white-cedar swamps could be increased substantially by drainage (44). Northern white-cedar generally grows more slowly and attains less height than associated trees, especially in swamps.

Information on yield of northern white-cedar is limited mainly to normal yield tables for pure, fully stocked, even-aged stands in the Lakes States. Such stands have yields at 120 years as shown in table 1 (27).

Table 1- Characteristics of fully stocked, even-aged stands of northern white-cedar in the Lakes States (27) Site index at base age 50 years Item 9 m or 30 ft 12 m or 40 ft Height of dominants and codominants, m     15   21 D.b.h., cm¹     23   31 Trees/ha¹ 1112 618 Basal area, m²/ha¹     45   47 Merchantable volume, m³/ha²   244 319 Sawtimber volume (Scribner), m³/ha³   129 279 Height of dominants and codominants, ft     50    69 D.b.h., in¹          8.9       12.4 Trees/acre¹   450  250 Basal area, ft²/acre¹   195  205 Merchantable volume, ft³/acre² 3,480  4,560   Sawtimber volume (Scribner), fbm/acre³ 9,220  19,900     ¹Trees 0.25 cm (0.1 in) and larger in d.b.h.
²Peeled volume for trees 13 cm (5.0 in) and larger in d.b.h.
³Volume for trees 23 cm (9.0 in) and larger in d.b.h. Northern white-cedar reaches a maximum basal area of about 69 m²/ha (300 ft²/acre) (8). Unfortunately for its value as timber, the tree commonly has a curved butt and poor form, especially in swamps (9).

Little is known about biomass production, although components of various-sized white-cedars have been analyzed for weight (and nutrient elements) (12). Above-ground biomass in one 70- to 100-year-old white-cedar stand totaled 159 t/ha (71 tons/acre) and had a net annual productivity of about 10 t/ha (4.5 tons/acre) (38).

Timber rotations for northern white-cedar differ greatly with site productivity and management objective. Rotations for maximizing merchantable cubic volume range from 70 to 90 years for a site index of 12 m (40 ft) and from 80 to 100 years for an index of 9 m (30 ft). Rotations for sawtimber range from 110 to 140 years for a site index of 12 m (40 ft) and from 130 to 160 years for an index of 9 m (30 ft) (27).

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Reaction to Competition

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Northern white-cedar is classed as shade tolerant, but it has been placed in three classes: very tolerant, tolerant, and intermediate. This variation probably exists because vegetative reproduction is considered more tolerant than seedlings (9). Northern white-cedar is less tolerant than balsam fir but slightly more tolerant than black spruce. White-cedar can withstand severe suppression for several years, and it responds well to release not only during the reproduction period but at nearly all ages (3,16).

Response to thinning northern white-cedar depends upon site quality, residual stand density, and stand age. In a well-drained Michigan swamp, a 45-year-old stand with a residual basal area of 15.8 m²/ha (69 ft²/acre) more than doubled its basal area in 8 years following thinning; a similar thinning in a poorly drained swamp showed no beneficial effect (16). In a 65-year-old stand on a medium swamp site in Wisconsin, basal area growth following a second thinning was independent of stand density over a wide range. The growth rate decreased following the second thinning, however, probably because of increasing stand age (14).

Both even-aged and uneven-aged stands of northern white-cedar are common. Even-aged stands develop in large swamp openings following wildfire or clearcutting (13). In Wisconsin white-cedar often invades speckled alder thickets that form in swamps following wildfire or changes in water level; and it can reproduce directly on burned peat (10). Even-aged stands also develop on abandoned upland fields in Maine (and southeastern Canada)- but apparently only where competition is not severe (9).

Uneven-aged white-cedar stands are generally associated with the late stages of succession and are found mainly in swamps or on other moist sites (23). They develop where white-cedar reproduces in small openings created by partial cutting or wind damage, especially on poor sites where reproduction is mainly of vegetative origin. Uneven-aged stands also develop where white-cedar gradually succeeds associates- such as balsam poplar, tamarack, and black spruce- that are not as shade tolerant or long-lived (13). However, understory white-cedars sometimes are not much younger than the overstory species; in such cases what appears to have developed through succession may really be due to suppression (23).

Without major disturbance such as fire, the northern white-cedar type is exceedingly stable because the tree is long-lived and balsam fir is the only important associate sufficiently shade tolerant to grow in dense white-cedar stands (10). Many stands, however, have been either opened by timber harvesting or severely browsed by white-tailed deer. In both cases, succession is often to balsam fir or swamp hardwoods, especially black ash (27).

In Michigan's Upper Peninsula, northern white-cedar reproduction was most abundant after clearcutting in small blocks and narrow strips, and it should grow best after such cutting because hardwood competition is less than after partial cutting (3). Shelterwood cutting is preferred, however, for the last blocks or strips to ensure adequate natural seeding (27). This method of cutting also provides the partial overstory shade necessary to reproduce white-cedar in areas with frequent hot, dry spells (19).

Successful deeryard management requires reproducing large, even-aged stands of white-cedar (47). Because deeryard management and timber management are usually inseparable in the white-cedar type, the general recommendation is to produce large patches- 16 to 65 ha (40 to 160 acres)- by harvesting small blocks annually (48), using clearcutting or shelterwood cutting as indicated above. Satisfactory reestablishment of white-cedar after clearcutting, however, often requires some kind of site preparation, particularly broadcast burning of slash (48). Where winter deer densities are high, the entire patch must be completely cleared in 10 years or less to minimize overbrowsing (27); but where they are low, small blocks or narrow strips may be clearcut at 30-year intervals (42).

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Rooting Habit

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Northern white-cedar seedlings grown in different soil media have shown that as moisture-holding capacity increases, root form changes from a long taproot with few laterals to shorter, thicker roots with many laterals. Root extension is particularly pronounced in rotten wood (9). In Wisconsin, seedlings grown from seed collected in upland stands developed deep root systems in well-drained soils and shallow root systems in saturated soils; their lowland counterparts showed little plasticity in root development (33).

After the seedling stage northern white-cedar generally develops a shallow, wide-spreading root system; and natural root grafts are fairly common. Because the tree grows on rocky cliffs throughout its range, the root system is apparently well adapted to secure water and nutrients from cracks in rocks (10).

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Seed Production and Dissemination

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Cone production has been induced within 3 months of seed germination using gibberellic acid and a long photoperiod (18). Under normal conditions cones have been found on northern white-cedars as young as 6 years old (9). Seed production in large quantities begins when the trees are about 30 years old but is best after 75 years. An average-sized tree with a fairly full crown can produce about 9 liters (0.25 bu) of cones (16), yielding 60,000 to 260,000 cleaned seeds. Limited data from Michigan indicate that white-cedar trees on upland sites produce more cones per tree, more seeds per cone, and a higher percentage of full seeds than those on swamp sites (6).

Rangewide, northern white-cedar generally bears good or better seed crops at intervals of 2 to 5 years. However, during a 26-year period (1949-74) in northeastern Wisconsin, such crops were produced every 1 to 3 years, with medium crops to failures in the intervening years. In addition, it was found that good or better white-cedar seed crops can be predicted by similar-sized crops in red maple the preceding spring (20).

Seed dispersal usually begins in September, although it sometimes begins as early as August. In the northern Lake States cones open from mid-September to late October (1,41). Most of the seeds are released by November, but some seeds continue to fall throughout the winter.

Northern white-cedar seeds are light chestnut brown, about 6 mm (0.25 in) long, and have lateral wings about as wide as the body; cleaned seeds average 763,000/kg (346,000/lb) (41). Most seed is wind disseminated, with the seeding range estimated to be from 45 to 60 m (150 to 200 ft) under normal conditions (16).

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Seedling Development

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Northern white-cedar seeds remain viable for 5 years or more when stored in sealed containers at 6 to 8 percent moisture content and 0° to 3° C (32° to 38° F). As a rule the seeds have only slight internal dormancy. Under forest conditions dormancy is broken while the seeds lie on the ground during the first winter; thus fall sowing is generally recommended (41). Because white-cedar seeds apparently do not remain viable in the forest floor longer than 1 year, such seeds should not be relied on for reproduction after clearcutting or fire (6,17).

Germination is epigeal, with the cotyledons rising above the ground. The seed seems to germinate best at high temperatures such as 29° C (84° F) (19), so that even though germination normally begins in May or June of the year following seed dispersal, it sometimes does not occur until late July or early August. Alternating day and night temperatures of 30° and 20° C (86° and 68° F), respectively, are recommended for germination tests (41).

Northern white-cedar seeds germinate readily on a variety of moist substrates, but seedlings become established on only a few. The main requirements for early development seem to be a constant moisture supply and warm temperatures (10,19). Although white-cedar generally grows best on neutral or slightly alkaline soil, seedlings do best on neutral or slightly acid soil but will grow on slightly alkaline soil (16). On cutover white-cedar swamps in Minnesota, seedlings were found only where the pH of the surface soil (upper 10 cm or 4 in) ranged from 6.6 to 7.2 (36).

On undisturbed areas, seedbeds of decaying (rotten) wood of logs and stumps account for more than 70 percent of the seedlings (10,25). These seedbeds usually are more moist, warmer, and have less litter than other seedbed types (19); they are also commonly dominated by mosses such as Heterophyllium, Pleurozium, and Brotherella (25). Some seedlings become established-but usually much less frequently-on decayed litter, peat or humus, and sphagnum moss.

On disturbed areas, northern white-cedar seedlings commonly prosper on both upland and swamp burns. Broadcast burning (or wildfire) apparently must be fairly severe, however, to expose favorable, mineral soil seedbeds on uplands or to improve moss seedbeds in swamps (27,48). White-cedar seedlings also reproduce well on skid roads where the compacted moss stays moist (16). A heavy cover of slash hinders seedling establishment, but a light cover is more favorable than none (27,48).

Northern white-cedar seedlings generally grow slowly under both forest and nursery conditions. Annual height growth averages only about 8 cm (3 in) during the first several years; seedlings can grow this much in 140 days under long photoperiods in growth chambers (18). Stock raised in a nutrient solution and hardened in a nursery was superior to 3-year-old (2-1) nursery transplants (49). In upland plantings transplants averaged 0.9 m (2.9 ft) tall at 9 years of age in the northern Lake States and 2.6 m (8.5 ft) tall at 12 years in Illinois (26,29).

Although moisture is often the most important factor during the first few years, ample light is needed for continued seedling development. Seedlings were tallest when grown in about half of full light, but their shoots and roots were heaviest in full light (31). In areas with frequent hot, dry spells, partial overstory shade is necessary to reduce losses from drought and herbaceous competition (19).

Both shoot and radial growth generally begin in May and end by late August or in September in the northern Lake States and New Brunswick (1,16).

Mortality of northern white-cedar seedlings during their early years is extremely high. Drought is probably the most important cause; seedlings on substrates such as thick moss, stumps, and hummocks often dry out during the summer. Other causes of early loss or damage include smothering by sphagnum moss or logging slash, cutting or girdling by small rodents such as the red-backed vole, and deer browsing (especially on planted stock) (9,16,26,49).

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Soils and Topography

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Northern white-cedar grows on a wide variety of organic soils (Histosols) and mineral soils (especially Inceptisols and Entisols); however, it does not develop well on extremely wet or extremely dry sites. It is most often associated with cool, moist, nutrient-rich sites, particularly on organic soils near streams or other drainage-ways, or on calcareous mineral soils. In Minnesota, however, white-cedar stands on uplands are primarily determined by an interaction of vegetation and lack of disturbance (21). Northern white-cedar commonly grows on soils ranging from pH 5.5 to 7.2 (9,36).

Northern white-cedar is usually dominant in rich swamps (forested rich fens) that have a strong flow of moderately mineral-rich soil water. The organic soil (peat) is usually moderately to well decomposed, 0.3 to 1.8 m (1 to 6 ft) thick, and often contains much rotted wood. It can also dominate the peat ridges in bog and fen complexes that have a sluggish movement of weakly enriched water (22).

On mineral soil (upland) sites northern white-cedar is characteristic of seepage areas, limestone uplands, and old fields. It is common on shallow loam over broken limestone in southeastern Ontario and often forms pure stands in old fields and pastures on moist, well-drained soils in Maine (9), southern Quebec, and southeastern Ontario. The tree also grows on calcareous clays, limestone cliffs, outcrops of acidic trap rock, and sandstone bluffs (10,29).

Northern white-cedar generally grows best on limestone-derived soils that are neutral or slightly alkaline and moist but well drained. Nevertheless, most commercial stands are in swamps, where northern white-cedar can compete well with its associates (13) and is normally protected from fire (23). Although old-field soils differ greatly, the tree's form and volume growth are much better on old fields than in poorly drained swamps (9).

Northern white-cedar grows from near sea level to more than 600 m (2,000 ft), but within most of its range it is found between 150 and 600 m (500 and 2,000 ft).

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Special Uses

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The principal commercial uses of northern white-cedar are for rustic fencing and posts; other important products include cabin logs, lumber, poles, and shingles. Smaller amounts are used for paneling, piling, lagging, pails, potato barrels, tubs, ties, boats (especially canoes), tanks, novelties, and woodenware (28). Recently, white-cedar has been used for making kraft pulp and it appears excellent for particleboard. "Cedar leaf oil" is distilled from boughs and used in medicines and perfumes; boughs are also used in floral arrangements (32).

The northern white-cedar type is valuable for wildlife habitat, particularly for deeryards during severe winters. The tree is highly preferred by white-tailed deer for both shelter and browse. Sapling stands produce a great amount of deer food (47) and clearcut stands in Michigan yielded almost 6000 kg/ha (5,340 lb/acre) of browse from tops (16). White-cedar is also utilized by such mammals as the snowshoe hare, porcupine, and red squirrel. Its browse is generally rated as highly preferred by hares (5,30) and is sometimes heavily utilized (6). Birds common in white-cedar stands during the summer include several warblers (northern parula, black-throated green, blackburnian, black-and-white, and magnolia), white-throated sparrows, and kinglets (9,11). The pileated woodpecker commonly excavates cavities in mature white-cedars to feed upon carpenter ants.

Northern white-cedar forms an attractive fringe around some lakes and peatlands. Stands with high basal area, large trees, and little undergrowth are especially attractive (35). The tree's unusual bark and foliage patterns are esthetically appealing to many forest users (27).

Northern white-cedar is widely used for ornamental plantings in the United States (24), is now common in Newfoundland, and has been grown in Europe since the 16th century. White-cedar is particularly useful for barrier and shelter plantings (29), and it is one of the few conifers recommended for power line rights-of-way (43).

Northern white-cedar has limited value as a watershed protector because it usually grows on gently sloping terrain. Although harvesting of white-cedar is presently on a small scale, clearcutting on peatland sites has little effect on annual water yields or water tables. Nutrient concentrations in streamflow or temperatures in trout streams should not increase significantly unless harvesting is on a massive scale (27,35).

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Vegetative Reproduction

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Northern white-cedar can send out roots from any part of a branch or stem if moisture conditions are favorable. Thus it frequently reproduces vegetatively in swamps, especially on poor sites with abundant sphagnum moss. If young seedlings are not considered, many more stems probably originate vegetatively than from seed in most swamps because vegetative reproduction is more tolerant of shade and is never without an adequate root system (9).

Layering generally accounts for more than half the stems of white-cedar reproduction in northern Michigan and Maine swamps. It is most common in young stands and those with leaning trees, where the lower branches become covered by moss. Seedlings may produce layerings by age 5 or before (16,34).

New trees also develop vegetatively from uprooted trees whose vertical branches form roots. Sprouts from roots or stumps are generally rare (16). Cuttings are commonly used to propagate cultivars of northern white-cedar; under forest conditions branchlets may be rooted by setting them out in deep sphagnum moss (9).

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Distribution

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The main range of northern white-cedar extends through the southern part of the eastern half of Canada and the adjacent northern part of the United States. Specifically, it extends westward from Anticosti Island in the Gulf of St. Lawrence to the southern part of James Bay and through central Ontario to southeastern Manitoba; then south through central Minnesota and Wisconsin to a narrow fringe around the southern tip of Lake Michigan; then east through southern Michigan, southern New York, central Vermont and New Hampshire, and Maine. The species also grows locally in northwestern Ontario, west-central Manitoba, southeastern Minnesota, southern Wisconsin, north-central Illinois, Ohio, southern New England, and in the Appalachian Mountains from western Pennsylvania south to western North Carolina and eastern Tennessee.


- The native range of northern white-cedar.

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Brief Summary

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Cupressaceae -- Cypress family

William F. Johnston

Northern white-cedar (Thuja occidentalis) is also called eastern white-cedar, arborvitae, and swamp-cedar. The name arborvitae or "tree of life" dates from the 16th century when the French explorer Cartier learned from the Indians how to use the tree's foliage to treat scurvy. A record tree in Michigan measures 175 cm (69 in) in d.b.h. and 34 m (113 ft) in height. The rot- and termite-resistant wood is used principally for products in contact with water and soil. The tree provides valuable shelter and browse in winter deeryards, and it is a widely planted ornamental.

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Physical Description

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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 yellow-green above, Leaves yellow-green below, Leaves not blue-green, 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.
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Thuja occidentalis

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Thuja occidentalis, also known as northern white-cedar,[1] eastern white-cedar,[2] or arborvitae,[2][3] is an evergreen coniferous tree, in the cypress family Cupressaceae, which is native to eastern Canada and much of the north-central and northeastern United States.[3][4] It is widely cultivated as an ornamental plant.

Common names

Its additional common names include swamp cedar,[3] American arborvitae,[4] and eastern arborvitae.[4] The name arborvitae is particularly used in the horticultural trade in the United States; it is Latin for 'tree of life' – due to the supposed medicinal properties of the sap, bark, and twigs.[5] It is sometimes called white-cedar (hyphenated) or whitecedar (one word)[4] to distinguish it from Cedrus, a distantly related genus of trees also known as cedars.[6]

Description

Unlike the closely related western red cedar (Thuja plicata), northern white cedar is only a small or medium-sized tree, growing to a height of 15 m (49 ft) tall with a 0.9 m (3.0 ft) trunk diameter, exceptionally to 38 metres (125 ft) tall and 1.8 metres (5.9 ft) diameter.[7] The tree is often stunted or prostrate in less favorable locations. The bark is red-brown, furrowed and peels in narrow, longitudinal strips. Northern white cedar has fan-like branches and scaly leaves. The foliage forms in flat sprays with scale-like leaves 3–5 millimetres (18316 in) long.

The seed cones are slender, yellow-green, ripening to brown, 9–14 millimetres (38916 in) long and 4–5 millimetres (532316 in) broad, with six to eight overlapping scales. They contain about eight seeds each.[7] The branches may take root if the tree falls.[4]

Taxonomy

The species was first described by Carl Linnaeus in 1753. Over 30 synonyms are listed in Kew's Plants of the World Online database.[8]

Distribution

Northern white cedar is native to an area in the southern part of eastern Canada and the adjacent part of the northern United States. It extends from southeastern Manitoba east throughout the Great Lakes region and into Ontario, Québec, New York, Vermont, New Hampshire, Maine, Prince Edward Island, New Brunswick, and Nova Scotia. Isolated populations occur in west-central Manitoba, and to the south in Massachusetts, Connecticut, Ohio, and Illinois and in the Appalachian Mountains of Kentucky, Tennessee, North Carolina, Pennsylvania, Maryland, Virginia, and West Virginia.[4] In Canada, its range reaches the Arctic treeline and the southern tip of Hudson Bay. It grows mainly in places with cooler summers, with a typical temperature of 16 to 22 °C (61 to 72 °F) in July, and a shorter growing season, from 90 to 180 days.[9]

Ecology

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A swamp along the Superior Hiking Trail in November with white cedars (left) and other trees and shrubs

Northern white cedar grows naturally in wet forests, being particularly abundant in coniferous swamps, where other larger and faster-growing trees cannot compete successfully. It also occurs on other sites with reduced tree competition, such as cliffs. Although not currently listed as endangered, wild white cedar populations are threatened in many areas by high deer numbers; deer find the soft evergreen foliage a very attractive winter food and strip it rapidly. The largest known specimen is 34 m (112 ft) tall and 175 cm (69 in) diameter, on South Manitou Island within Leelanau County, Michigan. Northern white cedars can be very long-lived trees in certain conditions, with notably old specimens growing on cliffs where they are inaccessible to deer and wildfire. As of 2008, the oldest known living specimen was 1,141 years old,[10] but a dead specimen with 1,653 growth rings has been found.[11] Despite their age, these very old trees are small and stunted due to the difficult growing conditions. These individuals' long lifespans have been attributed to their slow growth and their ability to survive when different sections of the tree are damaged or killed.[12] The Witch Tree, a T. occidentalis growing out of a cliff face on Lake Superior in Minnesota, was described by the French explorer Sieur de la Verendrye as being a mature tree in 1731; it is still alive today.

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Old trees growing on a rock ledge in Potawatomi State Park, Wisconsin

Specimens found growing on cliff faces in southern Ontario are the oldest trees in Eastern North America and all of Canada, having achieved ages in excess of 1,653 years.[4]

Uses

Thuja occidentalis is a tree with important uses in traditional Ojibwe culture. Honored with the name Nookomis Giizhik (Grandmother Cedar), the tree is the subject of sacred legends and is considered a gift to humanity for its myriad of uses, among them crafts, construction, and medicine.[13] It is one of the four plants of the Ojibwe medicine wheel, associated with the north. The foliage is rich in vitamin C and is believed to be the annedda, which cured the scurvy of Jacques Cartier and his party in the winter of 1535–1536.[9] Due to the presence of the neurotoxic compound thujone, internal use can be harmful if used for prolonged periods or while pregnant. It is commercially used for rustic fencing and posts, lumber, poles, shingles, and in the construction of log cabins.[9] It is the preferred wood for the structural elements, such as ribs and planking, of birchbark canoes and the planking of wooden canoes.[14]

The essential oil within the plant has been used for cleansers, disinfectants, hair preparations, insecticides, liniment, room sprays, and soft soaps. The Ojibwa reportedly made a soup from the inner bark of the soft twigs. Others have used the twigs to make teas to relieve constipation and headache.[14]

Cultivation

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A grove of a columnar ornamental variety in Powsin Botanical Garden, Warsaw, Poland

T. occidentalis is widely used as an ornamental tree, particularly for screens and hedges, in gardens, parks, and cemeteries. Over 300 cultivars exist, showing great variation in colour, shape, and size, with some of the more common ones being 'Degroot's Spire', 'Ellwangeriana', 'Hetz Wintergreen', 'Lutea', 'Rheingold', 'Smaragd' (or 'Emerald Green'), 'Techny', and 'Wareana'. It was introduced into Europe as early as 1540. These cultivars have gained the Royal Horticultural Society's Award of Garden Merit:

References

  1. ^ a b Farjon, A. (2013). "Thuja occidentalis". IUCN Red List of Threatened Species. 2013: e.T42262A2967995. doi:10.2305/IUCN.UK.2013-1.RLTS.T42262A2967995.en.
  2. ^ a b Brouillet L. et al. 2010+. "Thuja occidentalis Linnaeus". data.canadensys.net. Database of Vascular Plants of Canada (VASCAN). Retrieved 3 October 2020.
  3. ^ a b c "Thuja occidentalis". Germplasm Resources Information Network (GRIN). Agricultural Research Service (ARS), United States Department of Agriculture (USDA).
  4. ^ a b c d e f g Earle, Christopher J., ed. (2018). "Thuja occidentalis". The Gymnosperm Database.
  5. ^ Thuja, American Cancer Society, last revised 6/19/2007. available online
  6. ^ "The Cedars" (PDF). 2004.
  7. ^ a b Chambers, Kenton L. (1993). "Thuja occidentalis". In Flora of North America Editorial Committee (ed.). Flora of North America North of Mexico (FNA). Vol. 2. New York and Oxford. Retrieved 24 September 2016 – via eFloras.org, Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA.
  8. ^ "Thuja occidentalis L." Plants of the World Online. Royal Botanic Gardens, Kew. Retrieved 3 October 2020.
  9. ^ a b c Johnston, William F. (1990). "Thuja occidentalis". In Burns, Russell M.; Honkala, Barbara H. (eds.). Conifers. Silvics of North America. Washington, D.C.: United States Forest Service (USFS), United States Department of Agriculture (USDA). Vol. 1 – via Southern Research Station.
  10. ^ "Eastern OLDLIST. Thuja occidentalis". Rocky Mountain Tree-Ring Research, Inc. & Eastern Kentucky University. 2008. Retrieved 15 January 2021.
  11. ^ "Eastern OLDLIST a database of ancient trees and their ages". Rocky Mountain Tree-Ring Research, Inc. & Eastern Kentucky University. 2020. Retrieved 15 January 2021.
  12. ^ Larson, D.W. (2001). "The paradox of great longevity in a short-lived tree species". Experimental Gerontology. 36 (4–6): 651–673. doi:10.1016/S0531-5565(00)00233-3. ISSN 0531-5565. PMID 11295506. S2CID 24297929.
  13. ^ Geniusz, Wendy Makoons (2009). Our Knowledge is not Primitive. Syracuse, NY: Syracuse University Press
  14. ^ a b "USDA/NRCS Plant Guide: Northern White Cedar, Thuja occidentalis L." (PDF). United States Department of Agriculture. Retrieved 2008-02-15.
  15. ^ "RHS Plant Selector – Thuja occidentalis 'Danica'". RHS. Retrieved 5 March 2021.
  16. ^ "Thuja occidentalis 'Golden Tuffet'". RHS. Retrieved 5 March 2021.
  17. ^ "RHS Plant Selector – Thuja occidentalis 'Holmstrup'". RHS. Retrieved 5 March 2021.
  18. ^ "RHS Plant Selector – Thuja occidentalis 'Rheingold'". RHS. Retrieved 5 March 2021.
  19. ^ "RHS Plant Selector – Thuja occidentalis 'Smaragd'". RHS. Retrieved 5 March 2021.

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Thuja occidentalis: Brief Summary

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Thuja occidentalis, also known as northern white-cedar, eastern white-cedar, or arborvitae, is an evergreen coniferous tree, in the cypress family Cupressaceae, which is native to eastern Canada and much of the north-central and northeastern United States. It is widely cultivated as an ornamental plant.

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