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Thuja occidentalis L.


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    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
    Occurrence in North America
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    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].


    Habitat characteristics
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    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].
    Habitat: Cover Types
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    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
    Habitat: Ecosystem
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    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
    Habitat: Plant Associations
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    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
    Key Plant Community Associations
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    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]

General Ecology

    Fire Ecology
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    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].

    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".
    Fire Management Considerations
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    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].
    Growth Form (according to Raunkiær Life-form classification)
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    More info for the term: phanerophyte

    Immediate Effect of Fire
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    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.
    Life Form
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    More info for the term: tree

    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
    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
    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

    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
    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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    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].


    Management considerations
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    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

    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].


    Cover Value
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    Stands of northern white-cedar provide thermal cover for white-tailed
    deer, moose, and black bear [4,9,39].
    Importance to Livestock and Wildlife
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    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].
    Nutritional Value
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    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].
    Other uses and values
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    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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    Northern white-cedar browse is highly palatable to white-tailed deer
    Wood Products Value
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    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].


    Common Names
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    northern white-cedar
    northern whitecedar
    white cedar
    eastern white-cedar
    eastern arborvitae
    arbor vitae
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    The currently accepted scientific name for northern white-cedar is Thuja
    occidentalis L. [33].