Northern Ontario Plant Database

Plant Description

Thuja occidentalis L.

En: eastern white cedar, eastern arborvitae, northern white cedar, swamp cedar
Fr: thuja occidental, thuya du Canada, cèdre blanc, thuier cèdre
Oj: giizhik, gisheekandug, giizhikenh

Cupressaceae (Juniper or cypress Family)

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General: A slow-growing but long-lived, columnar, evergreen tree, usually 12—15 m tall, rarely taller in our area; somewhat shade tolerant and shallow rooted. The decay-resistant wood of eastern white cedar is often used for fence posts and shingles; its pale reddish-brown fragrant wood is also used for woodworking and cabinetry. Eastern white cedar is also a highly cultivated ornamental tree.

Stems/twigs: Young branches are flattened horizontally; twigs are 2-edged, green, glabrous, and completely covered by overlapping pairs of scale-like needles; young branches are an important food source for white-tailed deer. Trees can reproduce by layering and often have 2—3 main trunks. The bark is reddish-brown and shiny when young; mature trees have dull gray bark separating into elongate narrow interconnecting strips.

Needles: Evergreen, simple, and sessile. Needles of young branches are scale-like, crowded, lanceolate to broadly ovate, 1—2 mm long, somewhat fleshy, yellowish-green to green, flat, and arranged in 2 overlapping opposite pairs at each node (4-ranked), forming flat, fan-shaped sprays. The pair of needles on the upper and lower twig surface are flat and taper abruptly to a short point; the lateral pair of needles is folded lengthwise (keeled) and overlaps the side margins of the other pair; a prominent rounded resin gland is noticeable near the apex of each needle. Needles are persistent on older branches for several years; branch needles turn reddish-brown, elongate to 4—5 mm, and develop a sharply pointed (acuminate) apex.

Reproductive structures/cones: Unisexual, monoecious, with young male and female cones on the same branches. Pollen is produced in very small terminal male cones, 1—2 mm long, which have 2—6 pairs of overlapping scales. Female cones are erect and ellipsoid, 7—14 mm long, with 4—6 pairs of opposite, overlapping scales; cone scale margins are blunt to rounded. Immature seed cones are green; cones become brown, woody, and mature during the first growing season. Seed are elliptic, 4—7 mm long, with 2 transparent wings that surround the entire seed.

Habitat and Range: Swamps, moist to wet nutrient-rich lowland forests, streambanks, and shorelines; often growing over limestone bedrock or clays in upland sites. Eastern white cedar occurs throughout the Algoma District and across Ontario, as well as throughout eastern and southern Ontario. Native to boreal northeastern North America, eastern white cedar's Canadian range extends from Nova Scotia to Manitoba.

Similar Species: Eastern red cedar, which occurs in a few isolated areas in eastern and southern Ontario, is actually a species of juniper (Juniperus virginiana L.), rather than a cedar. Like eastern white cedar, trees grown in open areas, such as old fields, are columnar to pyramidal in shape, but are easily differentiated from cedar by their leaves and cones. Eastern red cedar has short scale-like leaves on young branches, but older stems have sharply pointed needle-like leaves; their cones are globose, fleshy, and blue with a pale whitish (glaucous) coating, similar to those of ground juniper (Juniperus communis L.).