Overview
AT A GLANCE
- Common Name: Western Redcedar
- Scientific Name: Thuja plicata
- Category: Plants
- Subcategory: Trees
- Size: 45 to 70 m (148 to 230 ft) height; trunk diameter up to 3 to 6 m (9.8 to 19.7 ft); ancient specimens exceed 75 m
- Weight: Mature standing tree biomass typically ranges from 20,000 to 100,000 kg (44,000 to 220,000 lb)
- Lifespan: 800 to 1,500 years; ancient rainforest giants exceed 1,800 to 2,000 years
- Diet: Photoautotrophic; oxygenic photosynthesis requiring high rainfall, humid maritime air, and deep, moist, acidic soils
- Habitat: Old-growth temperate rainforests, riparian river floodplains, and damp coastal valleys
- Range: Pacific Northwest of North America, from coastal Alaska south through British Columbia, Washington, Oregon, and northern California, with an interior disjunct population in the northern Rocky Mountains of Idaho and Montana
- Conservation Status: Least Concern
The Western Redcedar (Thuja plicata) is a colossal, monumental evergreen conifer belonging to the cypress family Cupressaceae, revered as the crowning giant of the Pacific Northwest temperate rainforests. Towering up to 230 feet into the mist with massive, fluted buttressed trunks that can span twenty feet in diameter, this majestic tree is celebrated by indigenous Coastal First Nations as the sacred ‘Tree of Life’ (*Cornerstone of Northwest Coast Indigenous Culture*).
Ecologically, Thuja plicata is a foundational keystone species of the Pacific rainforest biome, creating dense, cool, multi-tiered canopies that regulate watershed hydrology, stabilize salmon-spawning riverbanks, and provide vital winter thermal shelter and forage for elk and black-tailed deer. Its rot-resistant heartwood, rich in natural fungicidal and insecticidal thujaplicin compounds, resists decay for centuries even on the wet rainforest floor. Indigenous peoples used its wood and fibrous bark for everything from colossal ocean-going dugout canoes and monumental totem poles to woven clothing and waterproof baskets.
Biology and Physical Characteristics
The morphology of the Western Redcedar features an enormous, tapering trunk with a heavily fluted, buttressed base supporting an irregular, conical to pyramidal crown with gracefully drooping, J-shaped sweeping branches. Its bark is thin, stringy, and cinnamon-brown, shredding into long, fibrous vertical strips that peel away effortlessly. The foliage is composed of flattened, fern-like sprays of tiny, scale-like leaves arranged in opposite pairs, dark glossy green on top with faint, whitish stomatal butterfly patterns underneath, emitting a distinct, sweet, aromatic pineapple-like fragrance when crushed. The species is monoecious: male pollen cones are tiny and purplish; female seed cones are small, leathery, and egg-shaped, measuring 10 to 14 mm long, composed of 8 to 14 overlapping scales that open in autumn to release winged seeds. The heartwood is rich reddish-brown, saturated with natural tropolone-based thujaplicins that prevent fungal decay.
Behavior and Ecology
Extremely shade-tolerant, Western Redcedar seedlings can survive for decades in the dim understory of old-growth rainforests beneath Douglas-firs and Sitka spruces, waiting for a canopy gap to surge upward into the canopy. The tree develops an extensive, shallow root system that interlocks with neighboring trees and fungal mycorrhizal networks to withstand powerful Pacific winter gales. Its fallen trunks on the forest floor resist decay for over 500 years, serving as vital ‘nurse logs’ upon which hemlock and spruce seedlings germinate and take root.
Conservation and Human Impact
Currently assessed as Least Concern by the IUCN, the Western Redcedar remains widespread across the Pacific Northwest. However, centuries of aggressive commercial logging have eliminated over 90 percent of ancient old-growth cedar groves. In recent years, severe summer droughts and atmospheric warming in the Pacific Northwest have caused widespread ‘cedar dieback’ along low-elevation coastal margins, making it a focal point of climate resilience forestry.
Interesting Factoid
The Western Redcedar produces natural chemical compounds called thujaplicins that are so intensely antibacterial and antifungal that a fallen cedar log can lie on the soaking-wet rainforest floor for over 500 years without rotting.